View source for Wikipedia:Manual of Style/Dates and numbers

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FORMATTING: This page makes heavy and very particular use of a lot of specific formatting. To avoid confusion concerning the proper formatting of units, symbols, values, variables, code, etc., please observe the following markup conventions on this page:
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This page guides the presentation of numbers, dates, times, measurements, currencies, coordinates, and similar items in articles. The aim is to promote clarity, cohesion, and consistency, and to make the encyclopedia easier and more intuitive to use.

Where this manual gives options, maintain consistency within an article unless there is a good reason to do otherwise. The [[Wikipedia:Arbitration Committee|Arbitration Committee]] has ruled that editors should not change an article from one guideline-defined style to another without a substantial reason unrelated to mere choice of style; revert-warring over optional styles is unacceptable.{{efn|1=See Arbitration Committee statements of principles in cases on style-related edit warring in [[Wikipedia:Requests for arbitration/Jguk#Principles|June 2005]], [[Wikipedia:Requests for arbitration/jguk 2#Principles|November 2005]], and [[Wikipedia:Requests for arbitration/Sortan#Principles|February 2006]]; and [[Wikipedia:General sanctions/Units in the United Kingdom]].}} If discussion fails to resolve the question of which style to use in an article, defer to the style used by the first major contributor.
{{TOC limit|4}}

==General notes==
===Quotations, titles, etc.<span id="ExternException"></span>===

{{see also|Wikipedia:Manual of Style#Quotations}}

Quotations, titles of books and articles, and similar "imported" text should be faithfully reproduced, even if they use formats or units inconsistent with these guidelines or with other formats in the same article. If necessary, clarify via [bracketed interpolation], article text, or footnotes.

===Non-breaking spaces===

Guidance on the use of [[non-breaking space]]s ("hard spaces") is given in some sections below, but not all situations in which hard spaces ({{t|nbsp}} or <code>&amp;nbsp;</code>) or {{tlx|nowrap}} may be appropriate are described. {{crossref|For further information see {{section link|Wikipedia:Manual of Style|Non-breaking spaces}} and [[Wikipedia:Line-break handling]].}}

==Chronological items==
===Statements likely to become outdated===

{{Shortcut|MOS:DATED|MOS:CURRENT}}
{{See also|Wikipedia:Manual of Style/Words to watch#Relative time references|Wikipedia:As of}}

Except on pages updated regularly (e.g. [[Wikipedia:How the Current events page works|the "Current events" portal]]), terms such as {{!xt|now}}, {{!xt|currently}}, {{!xt|to date}}, {{!xt|so far}}, {{!xt|soon}}, and {{!xt|recently}} should usually be avoided in favor of phrases such as {{xt|during the 2010s}}, {{xt|since 2010}}, and {{xt|in August 2020}}. For current and future events, use phrases like {{xt|as of {{CURRENTMONTHNAME}} {{CURRENTYEAR}}}} or {{xt|since the beginning of {{CURRENTYEAR}}}} to signal the time-dependence of the information; use the template {{tl|as of}} in conjunction.

Relative-time expressions are acceptable for very long periods, such as geological epochs: {{xt|Humans diverged from other primates long ago, but [[q:Samuel Butler (novelist)#legislature|only recently developed state legislatures]].}}

{{anchors|Dates|dates|Years|years|Months|Dates and years|Dates, months and years}}

===Dates, months, and years===
{{shortcut|MOS:DATE|MOS:DATEFORMAT|MOS:YEAR}}
* These requirements do not apply to dates in quotations or titles; {{crossref|see {{section link|Wikipedia:Manual of Style|Quotations}}}}.
* Special rules apply to citations; {{crossref|see {{section link|Wikipedia:Citing sources|Citation style}}}}.
* See also [[Wikipedia:Overview of date formatting guidelines]].

====Formats<span id="Acceptable date formats"></span><span id="Date formats"></span>====

{| class="wikitable"
|+ Acceptable date formats
|-
! style="width:40pt;"<!--undersized width specification means actual column width determined by widest word/unbreakable string in the column-->| General use
! style="width:40pt;"| {{nowrap|Only in limited situations<br>where brevity is helpful}}{{efn|name=brevity|1=For use in tables, infoboxes, references, etc. Only certain citation styles use abbreviated date formats. By default, Wikipedia does not abbreviate dates. [[Wikipedia:Citing sources#Citation style|Use a consistent citation style within any one article.]]}}
! Comments<!--no width specification means this column will pick up all remaining horizontal width-->
|-
| {{xt|2{{nbsp}}September 2001}}
| {{xt|2{{nbsp}}Sep 2001}}
|
|-
| {{xt|September{{nbsp}}2, 2001}}
| {{xt|Sep{{nbsp}}2, 2001}}
| {{anchor|MDYCOMMA|MDY COMMA|mdy comma}} A comma follows the year unless [[Wikipedia:Manual of Style#Commas|followed by other punctuation that replaces the comma]]: {{unordered list| {{xt|The weather on March 12, 2005, was clear and warm}} | {{xt|Everyone remembers July{{nbsp}}20, 1969{{snd}}when humans first landed on the Moon }} }}
|-
| {{xt|2{{nbsp}}September}}
| {{xt|2{{nbsp}}Sep}}
| rowspan=2 | Omit year only where there is no risk of ambiguity: {{ unordered list | {{xt|The 2012 London Olympics ran from 25{{nbsp}}July to 12{{nbsp}}September}} | {{xt|January{{nbsp}}1 is New Year's Day}} }}
|-
| {{xt|September{{nbsp}}2}}
| {{xt|Sep{{nbsp}}2}}
|-
| {{nobr|<small>''No equivalent for {{nobr|general use}}''</small>}}
| {{xt|2001-09-02}}
| Use {{nowrap|{{var|yyyy}}-{{var|mm}}-{{var|dd}}}} format only with [[Gregorian calendar|Gregorian]] dates from 1583 onward.{{efn|1=All-numeric {{nowrap|{{var|yyyy}}-{{var|mm}}-{{var|dd}}}} dates might be assumed to follow the [[ISO 8601]] standard, which mandates the Gregorian calendar. Also, technically all years must have (only) four digits, but Wikipedia is unlikely to ever need to format a date beyond the year 9999.<!--don't astronomers deal with dates in the 5 digits or beyond?-->}}
|-
| {{xt|September 2001}}
| {{xt|Sep 2001}}
|
|}

{{shortcut|MOS:UNLINKDATES}}{{anchor|Date autoformatting|Autoformatting and linking|Linking and autoformatting of dates|Things to avoid}}
* Dates, years, and other chronological items should be linked only when they are relevant to the subject ''and'' likely to be useful to a reader; this rule does not apply to articles that are explicitly on a chronological item, e.g. [[2002]], [[19th century]] {{crossref|(as discussed at {{section link|Wikipedia:Linking|Chronological items}})}}.{{efn|1=The [[Wikipedia:Manual of Style/Dates and numbers/Date autoformatting|routine linking of dates]] is deprecated. This change was made August 24, 2008, on the basis of [[Wikipedia talk:Manual of Style (dates and numbers)/Archive D6#Again calling for date linking to be deprecated|this archived discussion]]. It was ratified in two December 2008 RfCs: [[Wikipedia:Manual of Style/Dates and numbers/Three proposals for change to MOSNUM]] and [[Wikipedia:Manual of Style/Dates and numbers/Date Linking RFC]].}}
* For issues related to dates in sortable tables, {{crossref|see {{section link|Help:Sorting|Configuring the sorting}}}} and {{crossref|{{section link|Help:Sorting|Date sorting problems}}}}, or consider using {{nowrap|{{tlx|dts|Nov 1, 2008}}.}}
* Phrases such as {{xt|[[Fourth of July]]}} (or {{xt|July{{nbsp}}Fourth}}, but not {{!xt|July{{nbsp}}4th}}), {{xt|[[Cinco de Mayo]]}}, {{xt|[[Seventh of March Speech]]}}, and {{xt|[[Independence Day (Brazil)|Sete de Setembro]]}} are proper names, to which rules for dates do not apply ({{xt|A typical Fourth of July celebration includes fireworks}}).

{{shortcut|MOS:DATESNO|MOS:BADDATE}}{{anchor|Unacceptable date formats}}
{| class="wikitable"
|+ Unacceptable date formats (except in [[#ExternException|external titles and quotes]])
|-
! style="width:95pt;"| [[File:X mark.svg|11px|link=|alt=]] Unacceptable
! style="width:80pt;"| [[File:Yes check.svg|11px|link=|alt=]] Corrected
! Comments
|-
|{{!xt|Sep'''.'''<!--←Bold to make dot more obvious.--> 2}}
|{{xt|Sep 2}}{{efn|name=brevity}}
|rowspan=2 | Do not add a dot to the day or to an abbreviated month.{{efn|1=For consensus discussion on abbreviated date formats like "Sep 2", see {{section link|Wikipedia talk:Manual of Style/Archive 151|RFC: Month abbreviations}}}}
|-
| {{!xt|9'''.'''<!--←Bold to make dot more obvious.--> June}}
| rowspan=5 | {{xt|9{{nbsp}}June}} or {{xt|June{{nbsp}}9}}
|-
| {{!xt|9 june}}<br />{{!xt|june 9}}
| Months are capitalized.
|-
| {{!xt|9th June}}<br />{{!xt|June 9th}}<br />{{nowrap|{{!xt|the 9th of June}}}}
| Do not use ordinals ({{!xt|1st}}, {{!xt|2nd}}, {{!xt|3rd}}, etc.).
|-
|{{!xt|09-06}}<br>{{!xt|06-09}}
| Do not use these formats.
|-
| {{!xt|09 June}}<br />{{!xt|June 09}}
| Do not zero-pad day{{nbsp}}...
|-
| {{!xt|2007-4-15}}
| rowspan=5| {{xt|2007-04-15}}{{efn|name=brevity}}
| ... except in all-numeric {{nowrap|({{var|yyyy}}-{{var|mm}}-{{var|dd}}) format}}, where both month and day should be zero-padded to two{{nbsp}}digits.
|-
| {{!xt|2007/04/15}}
| Do not use separators other than hyphens.
|-
| {{!xt|07-04-15}}
| Do not abbreviate year to two digits.
|-
| {{!xt|15-04-2007}}<br />{{!xt|04-15-2007}}<br />{{!xt|2007-15-04}}<!--The specific combination of values "04" and "15" (one below 12, the other above 12) used in these "Unacceptable" examples was chosen to allow there to be a single unambiguous entry in the "Acceptable" column.-->
| Do not use {{nowrap|{{var|dd}}-{{var|mm}}-{{var|yyyy}}}}, {{nowrap|{{var|mm}}-{{var|dd}}-{{var|yyyy}}}} or {{nowrap|{{var|yyyy}}-{{var|dd}}-{{var|mm}}}} formats.{{efn|1=These formats cannot, in general, be distinguished on sight, because there are usages in which ''{{nowrap|03-04-2007}}'' represents March{{nbsp}}4, and other usages in which it represents April{{nbsp}}3. In contrast, there is no common usage in which ''{{nowrap|2007-04-03}}'' represents anything other than April{{nbsp}}3.}}
|-
| {{!xt|2007 April 15}}<br />{{!xt|2007 Apr 15}}
| Do not use these formats.<!--the comment doesn't say "Do not put year first" because in yyyy-mm-dd format the year DOES go first-->
|-
| {{!xt|7/2001}}<br />{{!xt|7-2001}}<br />{{!xt|07-2001}}<br />{{!xt|2001-07}}<br />{{!xt|2001 July}}<br />{{!xt|July of 2001}}
| rowspan=2| {{xt|July 2001}}
| Do not use these{{nbsp}}formats.
|-
| {{!xt|July''',''' 2001}}
| rowspan=2| No comma between month and{{nbsp}}year.
|-
| {{!xt|3 July''',''' 2001}}
| {{xt|3{{nbsp}}July 2001}}
|-
| {{!xt|July 3 2001}}
| {{xt|July{{nbsp}}3''',''' 2001}}
| Comma required between day and{{nbsp}}year.
|-
| {{!xt|the{{nbsp}}'''{{'}}'''97 elections}}<br />{{!xt|the{{nbsp}}97 elections}}
| {{xt|{{nowrap|the 1997 elections}}}}
| Do not abbreviate year.
|-
| {{!xt|Copyright MMII}}
| {{xt|Copyright 2002}}
| [[Roman numerals]] are not normally used for{{nbsp}}dates.
|-
| {{!xt|{{nowrap|Two thousand one}}}}
| {{xt|2001}}
| rowspan=2| Years and days of the month are not normally written in{{nbsp}}words.
|-
| {{!xt|the first of May}}<br>{{!xt|May the first}}
| {{nowrap|{{xt|May{{nbsp}}1}} or {{xt|1{{nbsp}}May}}}}
|-
| {{!xt|June 0622}}
| {{xt|June 622}}
| Do not zero-pad years.
|-
| {{!xt|{{nowrap|sold in the year 1995}}}}
| {{xt|sold in 1995}}
| Write "the year" only where needed for clarity ({{xt|{{nowrap|About 1800 ships}} arrived in {{nowrap|the year 1801}}}}).
|}

=====Consistency=====

{{anchor|Format consistency}}
{{shortcut|MOS:DATEUNIFY}}
* '''Dates in article body text''' should all use the same format: {{xt|She fell ill on {{nobr|25 June 2005}} and died on {{nobr|28 June}}}}, not {{!xt|She fell ill on {{nobr|25 June 2005}} and died on {{nobr|June 28}}}}.
* '''Publication dates''' in an article's citations should all use the same format, which may be:
** the format used in the article body text,
** an abbreviated format from the [[#Dates and years|"Acceptable date formats" table]], provided the day and month elements are in the same order as in dates in the article body, or
** the format expected in the [[Wikipedia:Citing sources#Citation style|citation style]] being used (but all-numeric date formats other than {{nowrap|{{var|yyyy}}-{{var|mm}}-{{var|dd}}}} must still be avoided).
: For example, publication dates within a single article might be in one, but only one, of these formats (among others):
:: {{xt|Jones, J. (20 September 2008)}}
:: {{xt|Jones, J. (September 20, 2008)}}
* '''Access and archive dates''' in an article's citations should all use the same format, which may be:
** the format used for publication dates in the article (see above);
** the format expected in the citation style adopted in the article; or
** {{nowrap|{{var|yyyy}}-{{var|mm}}-{{var|dd}}}}
: For example, access/archive dates within a single article might be in one, but only one, of these formats (among others):
:: {{xt|Jones, J. (September 20, 2008){{nbsp}}... Retrieved February 5, 2009.}}
:: {{xt|Jones, J. (20 Sep 2008){{nbsp}}... Retrieved 5 Feb 2009.}}
:: {{xt|Jones, J. (20 September 2008){{nbsp}}... Retrieved 2009-02-05.}}
:When a citation style does not expect differing date formats, it is permissible to normalize publication dates to the article body text date format, and/or access/archive dates to either, with date consistency being preferred.

=====Strong national ties to a topic=====

{{shortcut|MOS:DATETIES}}

For any given article, the choice of date format and the choice of national variety of English (see {{section link|Wikipedia:Manual of Style#Strong national ties to a topic}}) are independent issues.
* Articles on topics with strong ties to a particular English-speaking country should generally use the date format most commonly used in that nation. For the United States this is (for example) {{nobr|{{xt|July 4, 1976}}}}; for most other English-speaking countries it is {{nobr|{{xt|4 July 1976}}}}.
* Articles related to Canada may use either format with (as always) consistency within each article. {{see below|Retaining existing format}}
*{{shortcut|WP:MILFORMAT}} In topics where a date format that differs from the usual national one is in customary usage, that format should be used for related articles: for example, articles on the modern US military, including biographical articles related to the modern US military, should use day-before-month, in accordance with US military usage.

=====Retaining existing format<span id="Retaining the existing format"></span>=====

{{shortcut|MOS:DATERET|MOS:DATEVAR}}
{{See also|Wikipedia:Manual of Style#Retaining existing styles}}
* If an article has evolved using predominantly one date format, this format should be used throughout the article, unless there are reasons for changing it based on strong national ties to the topic or consensus on the article's talk page.
* The date format chosen in the first major contribution in the early stages of an article (i.e., the first non-stub version) should continue to be used, unless there is reason to change it based on strong national ties to the topic or consensus on the article's talk page.
* Where an article has shown no clear sign of which format is used, the first person to insert a date is equivalent to "the first major contributor".

====Era style<span id="Year numbering systems"></span><span id="Eras and other very long periods"></span>====

{{Redirect|WP:BCE|the copyediting guide|Wikipedia:Basic copyediting}}
{{shortcut|MOS:ERA|MOS:BCE}}
* The default [[calendar era]]s are [[Anno Domini]] ({{xt|BC}} and {{xt|AD}}) and [[Common Era]] ({{xt|BCE}} and {{xt|CE}}). Either convention may be appropriate for use in Wikipedia articles depending on the article context. Apply {{section link|Wikipedia:Manual of Style|Retaining existing styles}} with regard to changes from one era to the other.
** Use either the BC{{ndash}}AD or the BCE{{ndash}}CE notation consistently within the same article. Exception: do not change [[MOS:QUOTE|direct quotations]], titles, etc.
** An article's established era style should not be changed without reasons specific to its content; seek consensus on the talk page first (applying {{section link|Wikipedia:Manual of Style|Retaining existing styles}}) by opening a discussion under a heading using the word ''era'', and briefly stating why the style should be changed.
** BCE and CE or BC and AD are written in upper case, unspaced, without a full stop (period), and separated from the numeric year by a space ({{xt|5{{nbsp}}BC}}, not {{!xt|5BC}}). It is advisable to use a [[Wikipedia:Manual of Style#Non-breaking spaces|non-breaking space]].
** AD appears before or after a year ({{xt|AD{{nbsp}}106}}, {{xt|106{{nbsp}}AD}}); the other abbreviations appear only after ({{xt|106{{nbsp}}CE}}, {{xt|3700{{nbsp}}BCE}}, {{xt|3700{{nbsp}}BC}}).
** In general, omit CE or AD, unless to avoid ambiguity or awkwardness
*** Typically, write {{xt|The [[Norman conquest of England|Norman Conquest]] took place in 1066}} not {{!xt|1066{{nbsp}}CE}} nor {{!xt|AD{{nbsp}}1066}}
*** But {{xt|[[Plotinus]] lived at the end of the 3rd century AD}} (not simply {{!xt|at the end of the 3rd century}}) may avoid confusion unless the era is clear from context.
*** One- and two-digit years may look more natural with an era marker ({{nobr|{{xt|born in 2{{nbsp}}AD}}}} or {{nobr|{{xt|born January 15, 22{{nbsp}}CE}}}}, not {{nobr|{{!xt|born in 2}}}} nor {{nobr|{{!xt|January 15, 22}}).}}
*** Ranges beginning in BC/BCE should specify the ending era: write {{nobr|{{xt|450 to 200 BCE}}}} or {{nobr|{{xt|450 BC to 200 BC}}}} or {{nobr|{{xt|450 BCE to 200 CE}}}}, but not {{nobr|{{!xt|450 BCE to 200}}}}. {{See below|Ranges}}
* '''Uncalibrated (BCE) radiocarbon dates:''' [[Calibrated years|Calibrated and uncalibrated]] dates can diverge widely, and some sources distinguish the two only via BCE or BC (for calibrated dates) versus bce or bc (uncalibrated). When feasible, avoid uncalibrated dates except in direct quotations, and even then ideally give the calibrated date in a footnote or square-bracketed note – {{xt|[3250&nbsp;BCE calibrated]}}, or at least indicate the date type – {{xt|[uncalibrated]}}. This also applies to other dating systems in which a calibration distinction in drawn.
* '''BP or YBP''': In scientific and academic contexts, BP (Before Present) or YBP (years Before Present) are often used. (''Present'' in this context by convention refers to January{{nbsp}}1, 1950.) Write {{xt|3000 years{{nbsp}}BP}} or {{xt|3000{{nbsp}}YBP}} or {{xt|3000{{nbsp}}years before present}} but not forms such as {{!xt|3000 before present}} and {{!xt|3000 years before the present}}. If one of the abbreviated forms is used, link to ''[[Before Present]]'' on first use: {{xt|The Jones artifact was dated to 4000{{nbsp}}[[before present|YBP]], the Smith artifact to 5000 YBP.}}
* {{anchor|Other_era_systems}}'''Other era systems''' may be appropriate in an article. In such cases, dates should be followed by a conversion to Anno Domini or Common Era, and the first instance linked: {{xt|Qasr-al-Khalifa was built in {{nobr|221{{nbsp}}[[Hijri year|AH]] (836{{nbsp}}CE)}}}}, or {{nobr|{{xt|in 836{{nbsp}}AD (221{{nbsp}}[[Hijri year|AH]])}}}}.
** [[Astronomical year numbering]] is similar to the Common Era. There is no need to follow a year expressed with astronomical year numbering with a conversion to Common Era. The first instance of a non-positive year should still be linked: {{xt|The March equinox passed into Pisces in [[Astronomical year numbering|year{{nbsp}}−67]].}} (The expressions {{xt|&minus;67}} and {{xt|68 BCE}} refer to the same year.)

====Julian and Gregorian calendars====

{{shortcut|MOS:OSNS|MOS:JG}}
{{see also|Old Style and New Style dates}}

A date can be given in any appropriate calendar, as long as it is (at the minimum) given in the [[Julian calendar]] or the [[Gregorian calendar]] or both, as described below. For example, an article on the early [[history of Islam]] may give dates in both [[Islamic calendar|Islamic]] and Julian calendars. Where a calendar other than the Julian or Gregorian is used, the article must make this clear.
* Current events are dated using the Gregorian calendar.
* Dates of events in countries using the Gregorian calendar at that time are given in the Gregorian calendar. This includes some of the [[Gregorian calendar#Timeline|Continent of Europe from 1582]], the [[British Empire]] from 14{{nbsp}}September 1752, and Russia from 14{{nbsp}}February 1918 {{crossref|(see [[Adoption of the Gregorian calendar]])}}.
* Dates before 15{{nbsp}}October 1582 (when the Gregorian calendar was first adopted in some places) are normally given in the Julian calendar.
* Dates after 4{{nbsp}}October{{nbsp}}1582 in a place where the Julian calendar was observed should be given in the Julian calendar.
* For either the Julian or Gregorian calendars, the beginning of the year should be treated as 1{{nbsp}}January even if a different start-of-year date was observed in the place being discussed.
* Dates for Roman history before 45{{nbsp}}BC are given in the [[Roman calendar]], which was neither Julian nor Gregorian. When (rarely) the Julian equivalent is certain, it may be included.
* For dates in early Egyptian and Mesopotamian history, Julian or Gregorian equivalents are often uncertain. Follow the consensus of reliable sources, or indicate their divergence.

The dating method used should follow that used by reliable secondary sources (or if reliable sources disagree, that used most commonly, with an explanatory [[Help:Footnotes|footnote]]). The guidance above is in line with the usage of reliable sources such as ''[[American National Biography]]'',<ref>{{cite encyclopedia | encyclopedia = American National Biography |title = Editorial note | date = 1999 | publisher = Oxford University Press | editor1-last = Garraty | editor1-first = John A. | editor2-last = Carnes | editor2-first = Mark C. | pages = xxi&ndash;xxii}}</ref> ''[[Oxford Dictionary of National Biography]]'', and ''[[Encyclopædia Britannica]]''{{efn|1=The calendar practices of ''Oxford Dictionary of National Biography'' and ''Encyclopædia Britannica'' can be inferred by looking up the birth and death dates of famous, well-documented individuals.}}

Where it's not obvious that a given date should be given in Julian alone or in Gregorian alone, consider giving both styles, for example by using {{tl|OldStyleDate}}. If a date appears without being specified as Old Style or New Style, tagging that date with {{tl|which calendar?}} will add the page to [[:Category:Articles containing ambiguous dates]] for further attention.

If an article contains Julian calendar dates after 4 October 1582 (as in the [[October Revolution]]), or if a start-of-year date other than 1 January was in force in the place being discussed, or both, a footnote should be provided on the first usage, explaining the calendar usage adopted for the article. The calendar usage should be compatible with this guideline.

====Ranges<span id="Date ranges"></span>====

{{anchors|Other date ranges|Dates of birth and death}}
{{shortcut|MOS:DATERANGE|MOS:DOB|MOS:YEARRANGE}}
{{See also|Wikipedia:Manual of Style#Number ranges}}
* A simple '''year{{ndash}}year''' range is written using an [[en dash]] (<code>–</code>, <code>&amp;ndash;</code> or {{tlx|ndash}}), not an em dash, hyphen, or slash; this dash is {{em|unspaced}} (that is, with no space on either side); and the end year is usually given in full:
** {{xt|1881{{ndash}}1882}};{{nbsp}} {{xt|1881{{ndash}}1886}} (not {{!xt|1881{{ndash}}86}});{{nbsp}} {{xt|1881{{ndash}}1992}} (not {{!xt|1881{{ndash}}92}})
** {{hanging indent|text=Markup: <code>1881{{tl|ndash}}1882</code> or <code>1881&amp;ndash;1882</code>}}
** Although non-abbreviated years are generally {{em|preferred}}, '''two-digit ending years''' ({{xt|1881{{ndash}}82}}, but never {{!xt|1881{{ndash}}882}} or {{!xt|1881{{ndash}}2}}) {{em|may}} be used in any of the following cases: (1) two consecutive years; (2) [[Wikipedia:Manual of Style/Infoboxes|infoboxes]] and tables where space is limited (using a single format consistently in any given table column); and (3) in certain topic areas if there is a very good reason, such as matching the established convention of reliable sources.{{efn|A change from a preference for two digits, to a preference for four digits, on the right side of ''year{{ndash}}year'' ranges was implemented in July 2016 per [[Special:Permalink/744053720#WP:DATERANGE ambiguity and stylistic concerns|this RFC]].<!--The change can be seen at https://en.wikipedia.org/?diff=744053720&oldid=744052603-->}} For consistency, avoid abbreviated year ranges when they would be used alongside non-abbreviated ranges within an article (or related pages, if in titles). Never use abbreviated years for ranges across centuries ({{xt|1999{{ndash}}2002}}, {{!xt|1999{{ndash}}02}}) or for years from the first millennium ({{xt|886{{ndash}}887}}, {{!xt|886{{ndash}}87}}).
** The '''{{visible anchor|slash notation}}''' ({{xt|2005/2006}}) may be used to signify a fiscal year or other special period, if that convention is used in reliable sources.
* Other "simple" ranges use an {{em|unspaced}} en dash as well:
** '''day{{ndash}}day''': {{xt|5{{ndash}}7{{nbsp}}January 1979}};{{nbsp}} {{xt|January{{nbsp}}5{{ndash}}7, 1979}};{{nbsp}} {{xt|elections were held March 5{{ndash}}8}}.
** '''month{{ndash}}month''': {{xt|the 1940 peak period was May{{ndash}}July}};{{nbsp}} {{xt|the peak period was May{{ndash}}July{{nbsp}}1940}};{{nbsp}} (but {{xt|the peak period was {{nobr|May 1940{{snd}}July}} 1940}} uses a {{em|spaced}} en dash; {{crossref|see below}})
* If at least one item on either side of the en dash contains a space, then a {{em|spaced}} en dash ({{tlx|snd}}) is used. For example:
** '''between specific dates in different months''': {{xt|They travelled {{nobr|June{{nbsp}}3{{snd}}August{{nbsp}}18,}} 1952}};{{nbsp}} {{xt|They travelled 3{{nbsp}}June{{snd}}18{{nbsp}}August 1952}}
** '''between dates in different years''':
*** {{xt|'''Charles Robert Darwin''' (12{{nbsp}}February {{nobr|1809{{snd}}19{{nbsp}}April}} 1882) was an English naturalist{{nbsp}}...}}
*** {{hanging indent|text=Markup: <code>12{{t|nbsp}}February 1809{{tl|snd}}19{{t|nbsp}}April 1882</code> or {{nowrap|<code>12&amp;nbsp;February 1809&amp;nbsp;&amp;ndash; 19&amp;nbsp;April 1882</code>}} }}
*** {{xt|'''Abraham Lincoln''' (February{{nbsp}}12, 1809{{snd}}April{{nbsp}}15, 1865) was the 16th President of{{nbsp}}...}}
** '''between months in different years''': {{xt|The exception was in force August {{nobr|1892{{snd}}January}} 1903}};{{nbsp}} {{xt|The Ghent Incursion (March 1822{{snd}}January{{nbsp}}1, 1823) was ended by the New Year's Treaty}}
*** {{hanging indent|text=Markup: <code>March 1822{{t|snd}}January{{t|nbsp}}1, 1823</code> or {{nowrap|<code>March 1822&amp;nbsp;&amp;ndash; January&amp;nbsp;1, 1823</code>}} }}
** Where '''era designations''', '''''circa''''' or '''other modifiers''' are present: {{nobr|{{xt|reigned 150 BCE{{snd}}50 BCE}}}}; {{nobr|{{xt|reigned 5 BC{{snd}}12 AD}}}}; {{nobr|{{xt|reigned c. 1393{{snd}}1414}}}}.<!--Hate to say it, but the text and examples leave unclear whether //150–50 BCE// or //150 – 50 BCE// is correct i.e. in the case in which an era designation is present only once, at the end--> {{See below|{{section link||Uncertain, incomplete, or approximate dates}}}}
{{shortcut|MOS:DATETOPRES|MOS:TOPRESENT}}{{anchors|Date range to present}}
* For ranges '''"to present"''', constructions such as {{nobr|{{xt|1982{{ndash}}present}}}} (with unspaced en dash), {{nobr|{{xt|January 1, 2011{{snd}}present}}}} (spaced ndash), or {{nobr|{{xt|January 2011{{snd}}present}}}} (spaced ndash) may be used, but other constructions may be more appropriate in prose {{crossref|(see {{section link||Statements likely to become outdated}})}}. In tables and infoboxes where space is limited, ''pres.'' may be used ({{xt|1982{{ndash}}pres.}}). Do not use incomplete-looking constructions such as {{nobr|{{!xt|1982{{ndash}}}}}} and {{nobr|{{!xt|1982{{ndash}}... }} .}}
**Consider adding the {{t|As of}} template to such constructions.
* <p>For a '''person still living''': {{xt|'''Serena Williams''' (born September{{nbsp}}26, 1981) is a{{nbsp}}...}}, not {{!xt|(September{{nbsp}}26, 1981{{snd}})}} or {{!xt|(born on September{{nbsp}}26, 1981)}}.</p><p>Do not use <code>*</code> to indicate ''born''; use <code>b.</code> only where space is limited e.g. tables and infoboxes; use either <code>born</code> or <code>b.</code> consistently in any given table column.</p>
* <p>Where '''birthdate is unknown''': {{xt|'''John Smith''' (died May{{nbsp}}1, 1622)}} or {{xt|'''John Smith''' (died 1622)}}</p><p>Do not use <code>†</code> to indicate ''died''; use <code>d.</code> only where space is limited, with consistency within any given table column.</p>
* <p>An '''overnight period''' may be expressed using a slash between two contiguous dates: {{xt|the night raids of 30/31{{nbsp}}May 1942}} or {{xt|raids of 31{{nbsp}}May{{nbsp}}/ 1{{nbsp}}June 1942}}.</p><p>Or use an en dash: (unspaced) {{xt|raids of 30{{ndash}}31{{nbsp}}May 1942}};{{nbsp}} (spaced) {{xt|raids of {{nobr|31{{nbsp}}May{{snd}}1{{nbsp}}June}} 1942}}.</p>
* Use an en dash, or a word such as ''from'' or ''between'', but not both: {{xt|from 1881 to 1886}} (not {{!xt|{{nobr|from 1881{{ndash}}1886}}}});{{nbsp}} {{xt|between June{{nbsp}}1 and July{{nbsp}}3}} (not {{!xt|{{nobr|between June{{nbsp}}1{{snd}}July{{nbsp}}3}}}})
* The {{tlx|Age}} template can keep ages current in infoboxes and so on:
** <code><nowiki>{{age|1989|7|23}}</nowiki></code> returns: {{xt|{{age|1989|7|23}}}}
** <code><nowiki>{{age|1989|7|23}}-year-old</nowiki></code> returns: {{xt|{{age|1989|7|23}}-year-old}}
** <code><nowiki>{{age|1989|7|23}} years old</nowiki></code> returns: {{xt|{{age|1989|7|23}} years old}}
* [[:Category:Date mathematics templates|Date mathematics templates]] are available for other age calculations.

====Uncertain, incomplete, or approximate dates====

<!--This section/anchor linked to from MOS:DATERANGE.-->
{{shortcut|MOS:APPROXDATE|MOS:CIRCA}}
* To indicate "around", "approximately", or "about", the use of the spaced, unitalicised form {{xt|c.{{nbsp}}1291}} (or the {{tlx|circa}} template) is preferred over {{!xt|circa}}, {{!xt|ca}}, {{!xt|ca.}}, {{!xt|around}}, {{!xt|approximately}}, or {{!xt|approx.}}:
** {{xt|At the birth of Roger Bacon (c. 1214){{nbsp}}...}}
** {{xt|'''John Sayer''' ({{circa|1750}}{{snd}}2{{nbsp}}October 1818){{nbsp}}...}}
** {{xt|the Igehalkid dynasty of Elam, {{circa|1400{{nbsp}}BC}}{{nbsp}}...}}
* Where both endpoints of a range are approximate, c. should appear before each date (the two-argument form of {{tlx|circa}} does this):
** {{xt|'''Dionysius Exiguus''' ({{circa|470|540}}{{nbsp}}...}} (not {{!xt|'''Dionysius Exiguus''' ({{circa}} 470{{snd}}540){{nbsp}}...}})
** {{xt|'''Rameses III''' (reigned {{circa|1180|1150{{nbsp}}BCE}}){{nbsp}}...}} (not {{!xt|'''Rameses III''' (reigned {{circa}} 1180{{snd}}1150{{nbsp}}BCE){{nbsp}}...}})
* Where birth/death limits have been inferred from known dates of activity:
** {{xt|'''Offa of Mercia''' (before 734{{snd}}26{{nbsp}}July 796){{nbsp}}...}}
** {{xt|'''Robert Menli Lyon''' (1789{{snd}}after 1863){{nbsp}}...}}
** {{xt|'''Ambrose Gwinnett Bierce''' (June 24, 1842{{snd}}after December 26, 1913){{nbsp}}...}}<!--Relationship between "before/after" and "fl." needs to be clarified.-->
* When birth and death dates are unknown, but the person is known to have been active ("flourishing") during certain years, {{xt|fl.}}, <code><nowiki>[[Floruit|fl.]]</nowiki></code>, or {{tlx|fl.}} may be used:
** {{xt|'''Jacobus Flori''' ([[floruit|fl.]]{{nbsp}}1571{{ndash}}1588) ...}}
: The linked forms should not be used on disambiguation pages, and "active" followed by the range is a better alternative for occupations not relating to the composition of works, whether it be musical, grammatical, historical, or any other such work.
* When a date is known to be either of two years (e.g. from a [[Regnal years of English monarchs|regnal]] or [[Hijri year|AH]] year conversion, or a known age at death):
** {{xt|'''Anne Smith''' (born 1912 or 1913; died 2013){{nbsp}}...}}
* Other forms of uncertainty should be expressed in words, either in article text or in a footnote: {{xt|April{{nbsp}}14, 1224 (unattested date)}}. Do not use a question mark ({{!xt|1291?}}), because it fails to communicate the nature of the uncertainty.
* Where {{xt|c.}}, {{xt|after}}, or a similar form appears ''which applies only to one of the two endpoints of the range'', use a spaced en dash (<code><nowiki>{{snd}}</nowiki></code>) and ideally a non-breaking space should follow very short modifiers such as {{xt|c.}}. ''Examples'': {{xt|{{nobr|1896{{snd}}after 1954}}}}, {{xt|{{nobr|{{c.|470|540}}}}}}. ''Markup:'' {{nobr|<code><nowiki>1896{{snd}}after 1954</nowiki></code>}}, {{nobr|<code><nowiki>{{c.|470|540}}</nowiki></code>}}.<!-- there's a {c} template as well-->
** If the modifier applies to the range as a whole, use an unspaced en dash: {{xt|[[floruit|fl.]]{{nbsp}}1571{{ndash}}1588}}; {{nobr|{{xt|traditionally 1571{{ndash}}1588}}}}.

===Times of day<span id="Time of day"></span>===

{{Shortcut|MOS:TIME|MOS:AMPM}}

Context determines whether the [[12-hour clock|12-]] or [[24-hour clock|24-hour]] clock is used. In all cases, colons separate hours, minutes, and (where present) seconds, e.g. {{xt|1:38:09{{nbsp}}pm}} or {{xt|13:38:09}}. Use figures ({{xt|11{{nbsp}}a.m.}} or {{xt|12:45{{nbsp}}p.m.}}) rather than words ({{!xt|twelve forty-five p.m.}}).
* '''12-hour clock times''' end with lower-case {{xtn|a.m.}} or {{xtn|p.m.}}, or {{xtn|am}} or {{xtn|pm}}, preceded by a [[#Non-breaking spaces|non-breaking space]], e.g. {{xt|2:30{{nbsp}}p.m.}} or {{xt|2:30{{nbsp}}pm}} (markup: <code>2:30{{tl|nbsp}}p.m.</code> or <code>2:30{{tl|nbsp}}pm</code>), not {{!xt|2:30p.m.}} or {{!xt|2:30pm}}. Hours should not have a leading zero (e.g. {{xt|2:30{{nbsp}}p.m.}}, not {{!xt|02:30{{nbsp}}p.m.}}). Usually, use {{xt|noon}} and {{xt|midnight}} rather than {{!xt|12 pm}} and {{!xt|12 am}}; whether "midnight" refers to the start or the end of a date should be explicitly specified unless clear from the context. Where several times that are all a.m. or all p.m. appear in close proximity, then ''a.m.'' or ''p.m.'' need be given only once if there is no risk of confusion.
* '''24-hour clock times''' have no a.m., p.m., noon or midnight suffix, and include a colon ({{xt|15:30}} not {{!xt|1530}}). Hours under 10 should have a leading zero ({{xt|08:15}}). The time {{xt|00:00}} refers to midnight at the start of a date, {{xt|12:00}} to noon, and {{xt|24:00}} to midnight at the end of a date, but {{!xt|24}} should not be used for the first hour of the next day (e.g. use {{xt|00:10}} for ten minutes after midnight, not {{!xt|24:10}}).

====Time zones====
{{shortcut|MOS:TIMEZONE}}
Give dates and times appropriate to the [[time zone]] where an event took place. For example, the date of the [[attack on Pearl Harbor]] should be December{{nbsp}}7, 1941 (Hawaii time/{{zwsp}}date). Give priority to the place at which the event had its most significant effects; for example, if a hacker in Monaco attacked a Pentagon computer in the US, use the time zone for the Pentagon, where the attack had its effect. In some cases, the best solution may be to add the date and time in [[Coordinated Universal Time]] (UTC). For example:

{{in5}}{{xt|8{{nbsp}}p.m. [[Eastern Standard Time (North America)|Eastern Standard Time]] on January{{nbsp}}15, 2001 (01:00{{nbsp}}UTC, January{{nbsp}}16)}}

Alternatively, include just the [[UTC offset]]:

{{in5}}{{xt|21:00{{nbsp}}[[British Summer Time]] ([[UTC+1]]) on 27{{nbsp}}July 2012}}

Rarely, the time zone in which an event took place has since changed; for example, China until 1949 was divided into [[Historical time zones of China|five time zones]], whereas all of modern China is [[UTC+8]]. Similarly, the term "UTC" is not appropriate for dates before this system was adopted in 1960;<ref>{{cite book |id=CCTF/09-32 |title=Coordinated Universal Time (UTC) |date=June 2, 2009 |publisher=[[Bureau International des Poids et Mesures]] |page=3 |quote=This coordination began on January 1, 1960, and the resulting time scale began to be called informally 'Coordinated Universal Time.'&thinsp; |url= http://www.bipm.org/cc/CCTF/Allowed/18/CCTF_09-32_noteUTC.pdf |format=PDF |access-date=August 20, 2015}}</ref> [[Universal Time]] (UT) is the appropriate term for the mean time at the [[prime meridian (Greenwich)]] when it is unnecessary to specify the precise definition of the time scale. Be sure to show the UTC or offset appropriate to the clock time in use at the time of the event, not the modern time zone, if they differ.

<span id="Day, month and season names"></span><span id="Longer periods"></span><span id="Other periods"></span><span id="Other"></span>

===Days of the week===

* Where space is limited (e.g. tables), days of the week may be abbreviated as {{xt|Sun}}, {{xt|Mon}}, {{xt|Tue}}, {{xt|Wed}}, {{xt|Thu}}, {{xt|Fri}}, {{xt|Sat}}.

===Seasons of the year<span id="Seasons"></span>===

<!--Wikipedia:Manual of Style/Words to watch#Relative time references links to this section.-->{{shortcut|MOS:SEASON}}
* Seasons are uncapitalized ({{xt|a hot summer}}) except when personified: {{xt|Jack Frost is a variant of Old Man Winter}}.
* Avoid the use of seasons to refer to a particular time of year ({{!xt|winter 1995}}) as such uses are ambiguous: the seasons are six months apart in the northern and southern hemispheres; winter in the northern hemisphere, and summer in the southern hemisphere, span two calendar years; and areas near the equator have only [[Wet season|wet]] and [[dry season]]s. Unambiguous alternatives include {{xt|early 1995}};{{nbsp}} {{xt|the first quarter of 1995}};{{nbsp}} {{xt|January to March 1995}};{{nbsp}} {{xt|spent the southern summer in Antarctica}}.
* Referring to a season by name is appropriate when it is part of a formal or conventional name or designation ({{xt|annual mid-winter festival}};{{nbsp}} {{xt|the autumn harvest}};{{nbsp}} {{xt|2018 Winter Olympics}};{{nbsp}} {{xt|''Times'' Fall Books Supplement}};{{nbsp}} {{xt|Details appeared in ''Quarterly Review'', Summer&nbsp;2015}};{{nbsp}} {{xt|The Court's winter term}}).

===Decades===

{{shortcut|MOS:DECADE}}
* To refer to a decade as a chronological period {{lang|la|per se}} (not with reference to a social era or cultural phenomenon), always use four digits as in {{xt|the{{nbsp}}1980s}}. Do not use {{!xt|the{{nbsp}}1980's}}, {{!xt|the{{nbsp}}1980{{nbh}}ies}}, or {{!xt|the{{nbsp}}1980s'}} (unless a possessive is actually meant).
** Prefixes should be hyphenated ({{xt|the{{nbsp}}mid{{nbh}}1980s}};{{nbsp}} {{xt|pre{{nbh}}1960s social attitudes}}).<!--Non-breaking hyphens {{nbh}} are used in some examples to keep them from being fragmented over linebreaks here in MOS; that's not to say {{nbh}} ought to be used in "real life" in such situations.-->
** Adjectives should not be hyphenated ({{xt|the late 1950s, the early 1970s}}).
* For a social era or cultural phenomenon associated with a particular decade:
** Two digits (with a preceding apostrophe) may be used as an alternative to four digits, {{em|but only if this is a well-established phrase seen in reliable sources}} ({{xt|the{{nbsp}}Roaring{{nbsp}}'20s}},{{nbsp}} {{xt|the{{nbsp}}Gay{{nbsp}}'90s}},{{nbsp}} {{xt|condemning the '60s counterculture}}, but {{xt|grew up in 1960s Boston, moving to Dallas in{{nbsp}}1971}}, and do not write {{!xt|the{{nbsp}}90's}};{{nbsp}} {{!xt|the{{nbsp}}90s}};{{nbsp}} or {{!xt|the{{nbsp}}90s'}}).
** A third alternative (where seen in reliable sources) is to spell the decade out, capitalized: {{xt|changing attitudes of the Sixties}}.

===Centuries and millennia<span id="centuries"></span><span id="millennia"></span>===

{{shortcut|MOS:CENTURY|MOS:MILLENNIUM}}

The sequence of numbered years in dates runs {{xt|...{{nbsp}}2{{nbsp}}BC, 1{{nbsp}}BC, 1{{nbsp}}AD, 2{{nbsp}}AD{{nbsp}}...}}; there is no "[[year zero]]".
* Treat the 1st century AD as years {{nobr|1{{ndash}}100}}, the 17th century as {{nobr|1601{{ndash}}1700}}, and the second millennium as {{nobr|1001{{ndash}}2000}}; similarly, the 1st century BC/BCE was {{nobr|100{{ndash}}1}} BC/BCE, the 17th century BC/BCE was {{nobr|1700{{ndash}}1601}} BC/BCE, and the second millennium {{nobr|2000{{ndash}}1001}} BC/BCE.
* Centuries and millennia are identified using either "Arabic" numerals ({{nobr|{{xt|the 18th century}}}}) or words ({{xt|the second millennium}}). When used adjectivally they contain a hyphen ({{xt|nineteenth-century painting}} or {{xt|{{nobr|19th-century}} painting}}). Do not use superscripts ({{!xt|19<sup>th</sup> century}}).
* Do not capitalize ({{!xt|the best Nineteenth-century paintings}};{{nbsp}} {{!xt|during the Nineteenth Century}})
* Do not use [[Roman numerals]] ({{!xt|XVIII{{nbsp}}century}}).
* {{xt|The 18th century}} refers to the period ({{nobr|1701{{ndash}}1800}}), while strictly {{!xt|the 1700s}} refers either to ({{nobr|1700{{ndash}}1799}}) or ({{nobr|1700{{ndash}}1709}})
** When using forms such as {{xt|the 1900s}}, ensure there is no ambiguity as to whether the century or just its first decade is meant.
* {{crossref|See {{section link|WP:Manual of Style|En dashes}} for use of hyphens and dashes in obscure situations.}}

===Long periods of time<span id="Abbreviations for long periods of time"></span>===

* When the term is frequent, combine {{xtn|yr}}{{nbsp}}(years) or {{xtn|ya}}{{nbsp}}(years ago) with {{xtn|k}}{{nbsp}}(thousand): {{xtn|kya}}, {{xtn|kyr}}; {{xtn|M}}{{nbsp}}(million): {{xtn|Mya}}, {{xtn|Myr}}; and {{xtn|b}}{{nbsp}}([[Long and short scales|short-scale]] billion): {{xtn|bya}}, {{xtn|byr}}. {{Crossref|(See {{section link|Year|Abbreviations yr and ya}} for more information.)}}
* In academic contexts, [[International System of Units|SI]] annus-based units are often used: {{xtn|ka}}{{nbsp}}(kiloannus), {{xtn|Ma}}{{nbsp}}(megaannus), and {{xtn|Ga}}{{nbsp}}(gigaannus). {{Crossref|(See {{section link|Year|SI prefix multipliers}} for more information.)}}
* Show the meaning parenthetically, and consider linking to the appropriate section of the [[Year]] article {{crossref|({{section link|Year|Abbreviations yr and ya}} or {{section link|Year|SI prefix multipliers}})}} on first occurrence and where the use is a standalone topic of interest. In source quotations, use square brackets: {{xt|"a measured Libby radiocarbon date of 35.1{{nbsp}}Mya [million years ago] required calibration{{nbsp}}..."}}

==Numbers==
===Numbers as figures or words===

{{shortcut|MOS:NUMERAL|MOS:SPELL09|MOS:MILLION|MOS:BILLION|MOS:TRILLION|MOS:LAKH|MOS:CRORE}}
{{crossref|Information on specific situations is scattered elsewhere on this page.}}

'''Generally, in article text:'''
* Integers from zero to nine are spelled out in words.
* Integers greater than nine {{em|expressible in one or two words}} may be expressed either in numerals or in words ({{xt|16}} or {{xt|sixteen}}, {{xt|84}} or {{nobr|{{xt|eighty-four}}}}, {{xt|200}} or {{nobr|{{xt|two hundred}}}}). When written as words, numbers from 21 to 99 are hyphenated (including when part of a larger number): {{nobr|{{xt|fifty-six}}}} or {{nobr|{{xt|fifty-six thousand}}}} but {{xt|five{{nbsp}}hundred}} or {{xt|five{{nbsp}}thousand}}.
* Other numbers are given in numerals ({{xt|3.75}}, {{xt|544}}) or in forms such as {{xt|21{{nbsp}}million}} (or ''billion'', ''trillion'', etc.{{snd}}but rarely ''thousand''). Markup: {{nowrap|<kbd><nowiki>21{{nbsp}}million</nowiki></kbd>}}
** ''Billion'' and ''trillion'' are understood to represent their [[Long and short scales|short-scale]] values of 10<sup>9</sup>{{nbsp}}(1,000,000,000) and 10<sup>12</sup>{{nbsp}}(1,000,000,000,000), respectively. Keep this in mind when translating articles from non-English or older sources.
** {{xt|M}} (unspaced, capitalized) or {{xt|bn}} (unspaced), respectively, may be used for "million" or "billion" after a number, when the word has been spelled out at the first occurrence ({{xt|Her estate of &pound;61{{nbsp}}million was split among her husband (&pound;1M), her son (&pound;5M), her butler (&pound;10M), and her three Weimaraners (&pound;15M each).}}).<!--This needs to be coordinated with text in units tables re nonuse of M (for 1000) MM, etc.-->
** SI prefixes and symbols, such as {{xtn|mega-}}{{nbsp}}({{xtn|M}}), {{xtn|giga-}}{{nbsp}}({{xtn|G}}) and {{xtn|tera-}}{{nbsp}}({{xtn|T}}), should be used only with units of measure as appropriate to the field and not to express large quantities in other contexts. Examples of misuse: {{!xt|In a population of 1.3G{{nbsp}}people, 300{{nbsp}}megadeaths would be expected.}}
** Sometimes, the [[Wikipedia:Manual of Style#National varieties of English|variety of English]] used in an article may suggest the use of a numbering system other than the Western thousands-based system. For example, the [[South Asian numbering system]] is conventionally used for certain things (especially monetary amounts) in [[South Asian English]]. This is discouraged in Wikipedia articles by {{section link|WP:Manual of Style#Opportunities for commonality}}.
*** When it is done anyway, for contextually important reasons, link the first spelled-out instance of each quantity (e.g. <code><nowiki>[[crore]]</nowiki></code>, which yields: [[crore]]). If no instances are spelled out, provide a note after the first instance, directing the reader to the article about the numbering system.
*** Provide a conversion to Western numbers for the first instance of each quantity (the templates {{tlx|lakh}}, {{tlx|crore}}, and {{tlx|lakh crore}} may be used for this purpose), and provide conversions for subsequent instances if they do not overwhelm the content of the article. For example, write {{xt|three [[crore]] (thirty million)}}. When converting a currency amount, use the exchange rate that applied at the time being written about; the {{tlx|INRConvert}} template can be used for this purpose.
*** Group digits in Western thousands-based style (e.g., {{xt|30,000,000}}; not {{!xt|3,00,00,000}}); {{crossref|see {{section link||Delimiting (grouping of digits)}}, below}}.
*** The variety of English does not uniquely determine the method of numbering in an article. Other considerations{{snd}}such as conventions used in mathematics, science, and engineering{{snd}}may also apply. The choice and order of formats and conversions is a matter of editorial discretion and consensus at the article.

{{anchor|Numeral notes}}{{shortcut|MOS:NUMNOTES}}
'''Notes and exceptions:'''
* Avoid beginning a sentence with a figure:
** Use: {{nowrap|{{xt|There were many matches''';''' 23 ended in a draw.}}}} Or: {{nowrap|{{xt|There were many matches'''.''' Twenty-three ended in a draw.}}}}
** Not: {{!xt|There were many matches'''.''' 23 ended in a draw.}}
** Use: {{xt|No elections were held in 1945 and 1950.}}
** Not: {{nowrap|{{!xt|1945 and 1950 had no elections.}}}} (Nor: {{nowrap|{{!xt|Nineteen forty-five and 1950 had no elections}} {{ndash}}}} comparable numbers should be both written in words or both in figures.)
** Opening a sentence with a proper name or technical term that begins with a numeral can usually be avoided by rewording:
*** Prefer: {{xt|Typically, 1-naphthylamine is synthesized via the Feldenshlager–Glockenspiel process.}} Or: {{xt|Feldenshlager{{ndash}}Glockenspiel is the process typically used in the synthesis of 1-naphthylamine.}}
*** Avoid: {{!xt|1-Naphthylamine is typically synthesized via the Feldenshlager{{ndash}}Glockenspiel process.}}
* In tables and infoboxes, quantities are expressed in figures ({{xt|Years in office:{{nbsp}}5}}); but numbers within a table's explanatory text and comments follow the general rule.
* Numbers in mathematical formulae are never spelled out ({{nobr|{{xt|3 < π < {{sfrac|22|7}}}}}}, not {{nobr|{{!xt|three < pi < twenty-two sevenths}}}}).
* Sport scores and vote tallies should be given as figures, even if in the zero-to-nine range ({{xt|a 25–7 victory}}; and {{xt|passed with 7 ayes, 2 nays, and 1 abstention}}).
* Comparable values should be all spelled out or all in figures, even if one of the numbers would normally be written differently: {{xt|patients' ages were five, seven, and thirty-two}} or {{xt|ages were{{nbsp}}5, 7, and{{nbsp}}32}}, but not {{!xt|ages were {{nobr|five, seven, and 32}}}}.<!--example using ages was chosen specifically, since questions about how to represent ages come up perennially-->
**Similar guidance applies where "mixed units" are used to represent a single value (as is often done with time durations, and in the imperial and US customary systems): {{xt|{{nobr|5 feet 11 inches}} tall}}; {{xt|{{nobr|five feet eleven inches}} tall}}; {{xt|{{nobr|3 minutes 27 seconds}}}}; {{xt|{{nobr|three minutes twenty-seven seconds}}}}.
* Adjacent quantities not comparable should ideally be in {{em|different formats:}} {{nobr|{{xt|twelve 90-minute volumes}}}} or {{nobr|{{xt|12 ninety-minute volumes}}}}, not {{nobr|{{!xt|12 90-minute volumes}}}} or {{nobr|{{!xt|twelve ninety-minute volumes}}}}.
** Avoid awkward juxtapositions: {{xt|On February 25, 2011, twenty-one more were chosen}}, not {{nobr|{{!xt|On February 25, 2011, 21 more were chosen}}}}.
* Sometimes figures and words carry different meanings; for example, {{xt|Every locker except one was searched}} implies there is a single exception (without specifying which), while {{xt|Every locker except{{nbsp}}1 was searched}} means that locker number{{nbsp}}1 was the only locker not searched.
* Proper names, technical terms, and the like are never altered: {{xt|[[10 Downing Street]]}},{{nbsp}} {{xt|[[Nine Inch Nails]]}},{{nbsp}} {{xt|[[Channel 8 (Thailand)|Channel 8]]}},{{nbsp}} {{xt|''[[Seven Samurai]]''}},{{nbsp}} {{xt|''[[The Sixth Sense]]''}},{{nbsp}} {{xt|[[Chanel No.&nbsp;5]]}},{{nbsp}} {{xt|[[Fourth Estate]]}},{{nbsp}} {{xt|''[[The Third Man]]''}},{{nbsp}} {{xt|[[Second Coming]]}},{{nbsp}} {{xt|[[First Amendment]]}},{{nbsp}} {{xt|''[[Zero Hour!]]''}},{{nbsp}} {{xt|[[Less Than Zero (song)|Less Than Zero]] }}
* Figures as figures: Use a figure when the figure itself (its [[glyph]], shape, etc.) is meant: {{xt|a figure-8 pattern}}; {{xt|in the shape of the numeral ''6''}}. {{crossref|(See {{section link|Wikipedia:Manual of Style/Text formatting#Words as words}}.)}}
* Only figures are used with unit {{em|symbols}} ({{xt|12 min}} not {{!xt|twelve min}}); but figures or words may be used with unit {{em|names}} ({{xt|12 minutes}} or {{xt|twelve minutes}}), subject to the provisions above.
{{shortcut|MOS:ORDINAL|MOS:1ST}}<!--Positioned before (rather than after) section in question to avoid crash of shortcut boxes when sections are short.-->

===Ordinals===

{{anchor|1st|1ST}}
{{redirect|MOS:1ST|the guideline on the first sentence in articles|MOS:FIRST}}
* For guidance on choosing between e.g. {{xt|15th}} and {{xt|fifteenth}}, see {{section link||Numbers as figures or words}}.
* In "suffix" forms, use two-letter suffixes: {{xt|1st, 2nd, 3rd, 4th}} and so on ({{xt|2nd{{nbsp}}Battalion}} not {{!xt|2d{{nbsp}}Battalion}}). Do not superscript ({{!xt|123<sup>rd</sup>}}).
* Do not use ordinals for dates (see [[MOS:BADDATE]]).
* In English text, do not use a dot ({{!xt|.}}) or the [[ordinal indicator]] ({{!xt|º}}). The masculine {{xt|º}} or feminine ({{xt|ª}}) ordinal indicator is acceptable in names, quotations, etc. from languages that conventionally use it. An Italian example: {{xt|{{lang|it|313º Gruppo Addestramento Acrobatico}}}} not {{!xt|313º Acrobatic Training Group}} or {{!xt|the 313º}}. Use HTML markup for languages that don't have a special character but conventionally use a superscript, like {{xt|{{lang|fr|2<sup>es</sup>}}}} in French.
* [[Regnal number]]s are normally written with ASCII [[Roman numeral]]s (without suffix, e.g. {{xt|Elizabeth II}} not {{!xt|Elizabeth IInd}} or {{!xt|Elizabeth 2nd}}).

===Number ranges===

{{shortcut|MOS:NUMRANGE|MOS:PAGERANGE}}

Like {{crossref|[[#Date ranges|date ranges]]}}, number ranges and page ranges should state the full value of both the beginning and end of the range, separated by an [[MOS:DASH|en dash]]: {{xt|pp.{{nbsp}}1902{{ndash}}1911}} or {{xt|entries{{nbsp}}342{{ndash}}349}}. Except in quotations, avoid abbreviated forms such as {{!xt|1902{{ndash}}11}} and {{!xt|342{{ndash}}9}}, which are not understood universally, are sometimes ambiguous, and can cause inconsistent metadata to be created in citations.

===Sport scores, vote tallies, etc.===

These use an unspaced {{t|ndash}}:
*{{tq|Smith beat Jones 7{{ndash}}3.}}
*{{tq|Polls predicted Alice would defeat Bob 74{{ndash}}20 percent, with 6 percent undecided.}}

===Singular versus plural===

* Nouns following [[simple fractions]] are singular ({{xt|took {{frac|4}} dose}};{{nbsp}} {{xt|net change was −{{frac|2}} point}};{{nbsp}} {{xt|{{frac|3|2}} dose}}).
* Nouns following [[mixed number]]s are plural ({{xt|1{{frac|1|2}} doses}};{{nbsp}} {{xt|another 4{{frac|3|4}} miles}}).
* Nouns following the lone, unsigned digit ''1'' are singular, but those following other decimal numbers (i.e. base-10 numbers not involving fractions) are plural ({{xt|increased 0.7 percentage points}};{{nbsp}} {{xt|365.25&nbsp;days}};{{nbsp}} {{xt|paid 5 dollars per work hour, 1 dollar per travel hour, 0 dollars per standby hour}};{{nbsp}} {{xt|increased by 1&nbsp;point}} but {{xt|net change +1&nbsp;points}};{{nbsp}} {{xt|net change &minus;1&nbsp;points}};{{nbsp}} {{xt|net change 1.0&nbsp;points}}).
* The same rules apply to numbers given in words ({{xt|one dose}};{{nbsp}} {{xt|one and one-half doses}};{{nbsp}} {{xt|zero dollars}};{{nbsp}} {{xt|net change of negative one points}}).

===Fractions and ratios<span id="Fractions"></span>===

{{shortcut|MOS:FRAC|MOS:RATIO}}
* Spelled-out fractions are hyphenated: {{xt|seven-eighths}}.
* Where numerator and denominator can each be expressed in one word, a fraction is usually [[Fractions#Pronunciation and spelling|spelled out]] (e.g. {{xt|a two-thirds majority}}; {{nbsp}}{{xt|moved one-quarter mile}}); use figures if a fraction appears with a symbol (e.g. {{xt|{{frac|1|4}}{{nbsp}}mi}}{{snd}}markup: <code>{{tlf|frac|1|4}}&amp;nbsp;mi</code>, not {{!xt|a quarter of a mi}} or {{!xt|one-quarter mi}}). A common exception is a series of values: {{xt|The distances were {{frac|1|1|4}}, {{frac|2|3}} and {{frac|1|2}} mile, respectively}}.
* [[Mixed numbers]] are usually given in figures, unspaced (not {{!xt|Fellini's film ''8{{nbsp}}{{frac|1|2}}''}} or {{!xt|''8-{{frac|1|2}}''}} but {{xt|Fellini's film ''{{frac|8|1|2}}''}}{{snd}}markup: <code><nowiki>{{frac|8|1|2}}</nowiki></code>). In any case the integer and fractional parts should be consistent (not {{!xt|nine and{{nbsp}}{{frac|1|2}}}}).
* Metric (SI) measurements generally use decimals, not fractions ({{xt|5.25{{nbsp}}mm}}, not {{!xt|5{{frac|1|4}}{{nbsp}}mm}}).
* Non-metric (imperial and US customary) measurements may use fractions or decimals ({{xt|5{{frac|1|4}}{{nbsp}}inches}};{{nbsp}}{{xt|5.25{{nbsp}}inches}}); the practice of reliable sources should be followed, and within-article consistency is desirable.
* In science and mathematics articles, mixed numbers are rarely used (use {{xt|{{sfrac|4|3}} the original}} rather than {{!xt|1{{sfrac|1|3}} times the original voltage}}). The use of {{tlx|frac}} [[Wikipedia:Manual of Style/Mathematics#Fractions|is discouraged]] in favor of one of these styles:
** <math>\textstyle\frac{1}{2}</math>{{snd}}markup: <code><[[WP:MATH|math]]>\textstyle\frac{1}{2}<nowiki></math></nowiki></code>
** {{xt|{{sfrac|1|2}}}}{{snd}}markup: {{tlx|sfrac|1|2}}
** {{xt|1/2}}{{snd}}markup: <code>1/2</code>
* Do not use precomposed fraction characters such as {{!xt|&frac12;}} (deprecated markup: <s><code>&amp;frac12;</code></s> or <s><code>&amp;#189;</code></s>). Exception: In special situations such as articles on [[chess]] matches, a precomposed ½ may be used if that is the only fraction appearing in the article.
* Ordinal suffixes such as {{xtn|-th}} should not be used with fractions expressed in figures (not {{!xt|each US state has 1/50th of the [[United States Senate|Senate's]] votes}}; {{!xt|1/8th mile}}, but {{xt|one-fiftieth of the [[United States Senate|Senate's]] votes}}; {{xt|1/8 mile}}; {{xt|one-eighth mile}}).
* Dimensionless ratios (i.e. those without accompanying units) are given by placing a colon between integers, or placing ''to'' between numbers-as-words: {{ xt|favored by a 3:1 ratio}} or {{nobr|{{ xt|a three-to-one ratio}}}}, not {{nobr|{{!xt|a 3/1 ratio}}}} or {{nobr|{{!xt|a 3&ndash;1 ratio}}.}}
** Use a colon (spaced) when one or more decimal points is present {{nobr|({{ xt|a 3.5&nbsp;:&nbsp;1 ratio}}{{snd}}markup:}} {{nobr|<code>a 3.5&amp;nbsp;:&amp;nbsp;1 ratio</code>).}}
** Do not use the colon form where units are involved ({{!xt|dissolve using a {{nobr|3 ml : 1 g ratio}}}}){{mdashb}}instead see ''ratios'' section of table at [[#Unit names and symbols|§&nbsp;Unit names and symbols]], below.

===Decimals<span id="Decimal points"></span>===

{{shortcut|WP:DECIMAL|MOS:DECIMAL}}
* Use a period/full point (<code>.</code>) as the [[decimal separator]], {{em|never}} a comma: {{xt|6.57}}, not {{!xt|6,57}}.
* Numbers between −1 and +1 require a leading zero ({{xt|0.02}}, not {{!xt|.02}}); exceptions are sporting performance averages ({{xt|.430 [[batting average (baseball)|batting average]]}}) and commonly used terms such as {{xt|.22{{nbsp}}caliber}}.
* Indicate repeating digits with an [[Vinculum (symbol)|overbar]] e.g. {{nowrap|<code><nowiki>14.31{{overline|28}}</nowiki></code>}} gives {{xt|14.31{{overline|28}}}}. (Consider explaining this notation on first use.) Do not write e.g. {{nobr|{{!xt|14.31(28)}}}} because it resembles [[#Uncertainty|notation for uncertainty]].

===Grouping of digits===

<span id="Delimiting (grouping of digits)"></span><span id="Grouping of digits"></span>
{{shortcut|WP:DIGITS|MOS:DIGITS}}
* Digits should be grouped and separated either by commas or by narrow gaps ({{em|never}} a period/full point).
** Grouping with commas
*: Left of the decimal point, five or more digits are grouped into threes separated by commas (e.g. {{xt|12,200}}; {{xt|255,200&nbsp;km}}; {{xt|8,274,527th}}; {{xt|{{frac|86,400}}}}).
*: Numbers with exactly four digits left of the decimal point may optionally be grouped (either {{xt|1,250}} or {{xt|1250}}), with consistency within any given article.
*: When commas are used left of the decimal point, digits right of the decimal point are not grouped (i.e. should be given as an unbroken string).
*: Markup: {{tlc|[[Help:Parser functions|formatnum:]]}} produces this formatting.
** Grouping with narrow gaps
*: Digits are grouped both sides of the decimal point (e.g. {{xt|{{val|6543210.123456}}}}; {{xt|{{val|520.01234|u=degC}}}}; {{xt|{{sfrac|{{val|101325}}|760}}}}).
*: Digits are generally grouped into threes. Right of the decimal point, {{em|usual}} practice is to have a final group of four in preference to leaving an "orphaned" digit at the end ({{xt|{{val|99.1234567}}}}, but {{xt|{{gaps|99.123|456|7}}}} would also be acceptable). In mathematics-oriented articles long strings may be grouped into fives (e.g. {{xt|{{gaps|3.14159|26535|89793|23846|...}}}}).
*: This style is especially recommended for articles related to science, technology, engineering or mathematics.
*: Markup: Templates {{tlx|val}} or {{tlx|gaps}} may be used to produce this formatting. Note that use of {{em|any}} space character as a separator<!--Word included here on purpose, for in-page searching.--> in numbers, including non-breaking space, is problematic for [[screen reader]]s. {{crossref|(See {{section link||Non-breaking spaces}}.)}} Screen readers read out each {{em|group}} of digits as separate numbers (e.g. <code>30{{tl|thin space}}000</code> is read as "thirty zero zero zero".)
* Delimiting style should be consistent throughout a given article.
** Either use commas or narrow gaps, but not both in the same article.
** Either group the thousands in a four-digit number or do not, but not mixed use in the same article.
** However, grouping by threes and fives may coexist.
* An exception is made for four-digit page numbers or four-digit calendar years. These should never be grouped (not {{!xt|sailed in 1,492}}, but {{xt|dynasty collapsed around 10,400&nbsp;BC}} or {{xt|by {{val|13727|u=AD}}, Vega will be the northern pole star}}).

===Percentages===

{{shortcut|MOS:PERCENT|WP:PERCENT|WP:%}}
* In the body of non-scientific/non-technical articles, {{xtn|percent}} (American English) or {{xtn|per cent}} (British English) are commonly used: {{xt|10 percent}}; {{xt|ten percent}}; {{xt|4.5 per cent}}. Ranges are written {{xt|ten to twelve per cent}} or {{xt|ten to twelve percent}}, not {{!xt|ten{{ndash}}twelve per cent}}.
* In the body of scientific/{{zwsp}}technical articles, and in {{em|tables and infoboxes}} of any article, the symbol <code>%</code> (unspaced) is more common: {{xt|3%}}, not {{!xt|3{{nbsp}}%}} or {{!xt|three{{nbsp}}%}}. Ranges: {{xt|10{{ndash}}12%}}, not {{!xt|10%{{ndash}}12%}} or {{nobr|{{!xt|10 to 12%}}}}.
* When expressing the difference between two percentages, do not confuse a percentage change with a change in [[percentage point]]s.

===Scientific and engineering notation<span id="Scientific notation, engineering notation, and uncertainty"></span>===

* [[Scientific notation]] always has a single nonzero digit to the left of the point: not {{!xt|{{val|60.22|e=22}}}}, but {{xt|{{val|6.022|e=23}}}}.
* [[Engineering notation]] is similar, but with the exponent adjusted to a multiple of three: {{xt|{{val|602.2|e=21}}}}.
* Avoid mixing scientific and engineering notations ({{!xt|A {{val|2.23|e=2|u=m2}} region covered by {{val|234.0|e=6|u=grains of sand}}}}).
* In a table column (or other presentation) in which all values can be expressed with a single power of 10, consider giving e.g. {{xt|{{e|7}}}} once in the column header, and omitting it in the individual entries. (Markup: <code><nowiki>{{e|7}}</nowiki></code>)
* In both notations, the number of digits indicates the precision. For example, {{xt|{{val|5|e=3}}}} means rounded to the nearest thousand; {{xt|{{val|5.0|e=3}}}} to the nearest hundred; {{xt|{{val|5.00|e=3}}}} to the nearest ten; and {{xt|{{val|5.000|e=3}}}} to the nearest unit.

Markup: {{tlx|val}} and {{tlx|e}} may be used to format exponential notation.

===Uncertainty and rounding <span id="Uncertainty"></span> <span id="Large numbers"></span>===

{{shortcut|MOS:UNCERTAINTY|MOS:LARGENUM}}
* Where explicit uncertainty information (such as a [[margin of error]]) is available and appropriate for inclusion, it may be written in various ways:
** {{xt|(1.534 ± 0.035) × 10<sup>23</sup> m}}
** {{xt|12.34{{nbsp}}m<sup>2</sup> ± 5%}} (not used with scientific notation)
** {{xt|15.34 {{su|p=+0.43|b=−0.23}} × 10<sup>23</sup> m}}
** {{xt|1.604(48) × 10<sup>−4</sup> J}} (equivalent to {{xt|(1.604 ± 0.048) × 10<sup>−4</sup> J}}){{efn|1=The number in parentheses in a construction like {{xt|1.604(48) × 10<sup>−4</sup> J}} is the numerical value of the standard uncertainty referred to the corresponding last digits of the quoted result.<ref>{{cite web |url= http://www.physics.nist.gov/cgi-bin/cuu/Info/Constants/definitions.html |title=Fundamental Physical Constants: Standard Uncertainty and Relative Standard Uncertainty |work=The NIST Reference on Constants, Units, and Uncertainty |date=June 25, 2015<!--Last updated, according to https://physics.nist.gov/cuu/Constants/bibliography.html --> |publisher=US [[National Institute of Standards and Technology]] |access-date=December 12, 2017}}</ref>}}
** {{xt|Polls estimated Jones's share of the vote would be 55 percent, give or take about 3 percent}}
** Markup: {{tlx|+-}}, {{tlx|su}}, and {{tlx|val}} may be used to format uncertainties.
* Where explicit {{em|uncertainty is unavailable}} (or is unimportant for the article's purposes) round to an appropriate number of [[significant digit]]s; the precision presented should usually be conservative. Precise values (often given in sources for formal or matter-of-record reasons) should be used only where stable and appropriate to the context, or significant in themselves for some special reason.
** {{xt|The speed of light is defined to be 299,792,458{{nbsp}}m/s}}
** {{em|but}} {{xt|Particle velocities eventually reached almost two-thirds the 300-million-metre-per-second speed of light.}}
** {{xt|checks worth $250 (equivalent to $1,800 in 2016)}} (not {{!xt|$1,845.38 in 2016}})
** {{xt|The city's 1920 population was 10,000}} (not {{!xt|population was 9,996}}{{snd}}an official figure unlikely to be accurate at full precision)
** {{em|but}} {{xt|The town was ineligible because its official census figure (9,996) fell short of the statutory minimum of ten thousand }} (unusual case in which the full-precision official figure is truly informative)
** {{xt| The accident killed 337 passengers and crew, and 21 people on the ground }} (likely that accurate and precise figures were determined)
** {{xt| At least 800 persons died in the ensuing mudslides }} (unlikely that any precise number can be accurate, even if an official figure is issued)
** {{em|or}} {{xt| Officials listed 835 deaths, but the Red Cross said dozens more may have gone unreported }} (in reporting conflicting information, give detail sufficient to make the contrast intelligible)
** {{xt|The jury's award was $8.5{{nbsp}}million}} (not {{!xt|$8,462,247.63}}). {{xt|The appeals court reduced this to $3,000,001 (one dollar in actual damages, the remainder in punitive damages).}}
* The number of decimal places should be consistent within a list or context ({{xt|The response rates were 41.0 and 47.4 percent, respectively}}, not {{!xt|41 and 47.4 percent}}), unless different precisions are actually intended.
* It may sometimes be appropriate to note the {{em|lack}} of uncertainty information, especially where such information is normally provided and necessary for full interpretation of the figures supplied.
** {{xt|A local newspaper poll predicted 52 percent of the vote would go to Smith, but did not include information on the uncertainty of this estimate}}
* The {{tlx|undue precision}} template may be added to figures appearing to be overprecise.
* Avoid using "approximately", "about", and similar terms with figures that have merely been approximated or rounded in a normal and expected way, unless the reader might otherwise be misled.
** {{xt|The tallest player was 6 feet 3 inches}} ({{nobr|not {{!xt|... about 6 feet 3 inches}}}}{{snd}}heights are conventionally reported only to the nearest inch, even though greater precision may be available in principle)<!--Please, no lectures about SI – if you can give a parallel metric example please do so.-->
** {{em|but}} {{xt|The witness said the assailant was about 5 feet 8 inches tall}} ("about" because here the precise value is unknown, with substantial uncertainty)
* The reader may be assumed to interpret large round numbers ({{xt|100,000 troops}}) as approximations. Writing a quantity in words ({{xt|one hundred thousand troops}}) can further emphasize its approximate nature.
* {{crossref|See {{section link||Unit conversions}} below for precision issues when converting units.}}

===Non–base 10 notations===

{{shortcut|MOS:BASE|MOS:RADIX|MOS:BINARY|MOS:HEX}}
* In computer-related articles, use the prefix <code>0x</code> for hexadecimal and <code>0b</code> for binary,{{efn|1=The <code>0x</code>, but not <code>0b</code>, is borrowed from the [[C (programming language)|C programming language]].}} unless there is a strong reason to use some other notation.{{efn|1=One such situation is with [[Unicode]] codepoints, which use <code>U+</code>; {{xt|U+FDD0}}, not {{!xt|0xFDD0}}.}} Explain these prefixes in the article's introduction or on first use.
* In all other articles, use base: {{base|137|9}}, {{base|201|3}}. Markup: <code><nowiki>{{base|137|9}}</nowiki></code>, <code><nowiki>{{base|201|3}}</nowiki></code>
* For [[Radix|bases]] above 10, use symbols conventional for that base (as seen in reliable sources) e.g. for [[base 16]] use {{nobr|0{{ndash}}9 and A{{ndash}}F}}.
* For octal, use {{base|200|8}}. Avoid using a prefix unless it is needed for computer code samples, in which case explain the prefix on first use.

===Mathematical formulae===

{{Main|Wikipedia:Manual of Style/Mathematics}}

There are multiple ways to display mathematical formulae, covered in detail at {{section link|Wikipedia:Manual of Style/Mathematics#Typesetting of mathematical formulae}}. One uses special MediaWiki {{tag|math}} markup using [[LaTeX]] syntax, which is capable of complex formulae; the other relies on conventionalized [[HTML]] formatting of simple formulae.

The {{tag|math|o}} markup is displayed as a [[Portable Network Graphics|PNG]] image by default. Logged-in users can optionally have it rendered in [[MathML]], or in HTML (via [[MathJax]]); detailed instructions are at [[Help:Displaying a formula]].

[[Wikipedia:Manual of Style#Section headings|Do not put {{tag|math|o}} markup in headings]].

==Units of measurement==

{{Shortcut|MOS:UNIT|MOS:UNITS|MOS:METRIC|MOS:MEASUREMENT}}

===Unit choice and order===

Quantities are typically expressed using an appropriate "primary unit", displayed first, followed, when appropriate, by a conversion in parentheses e.g. {{xt|{{convert|200|km|mi}}}}. For details on when and how to provide a conversion, see the section {{section link||Unit conversions}}. The choice of primary units depends on the circumstances, and should respect the principle of "[[Wikipedia:Strong national ties|strong national ties]]", where applicable:
* In '''non-scientific articles with strong ties to the United States''', the primary units are [[United States customary units|US customary]] (pounds, [[statute mile|miles]], feet, inches, etc.)
* In '''non-scientific articles with strong ties to the United Kingdom''', the primary units for most quantities are metric or other internationally used units,{{efn|1=If there is disagreement about the primary units used in a UK-related article, discuss the matter on the article talk-page or at [[Wikipedia talk:Manual of Style/Dates and numbers]] ([[WT:MOSNUM]]). If consensus cannot be reached, refer to historically stable versions of the article and retain the units used in these as the primary units. Also note the [[Metrication in the UK#Newspapers|style guides]] of British publications (e.g. [https://web.archive.org/web/20110918050646/http://www.timesonline.co.uk/tol/tools_and_services/specials/style_guide/article986731.ece ''The Times''], under "Metric").}} except that:
** UK engineering-related articles, including those on bridges and tunnels, generally use the system of units in which the subject project was [[engineering drawing|drawn up]] (but road distances are given in imperial units, with a metric conversion{{snd}}see next bullet);
** the primary units for distance/{{zwsp}}length, speed and fuel consumption are [[statute mile|miles]], miles per hour, and miles per imperial gallon (except for short distances or lengths, where miles are too large for practical use);
** the primary units for personal height and weight are feet{{zwsp}}/inches and stones/{{zwsp}}pounds;
** imperial pints are used for quantities of draught beer/{{zwsp}}cider and bottled milk;
* In '''all other articles''', the primary units chosen will be [[International System of Units|SI]] units, [[Non-SI units mentioned in the SI|non-SI units officially accepted for use with the SI]], or such other units as are conventional in reliable-source discussions of the article topic (such as [[revolutions per minute]] (rpm) for [[rotational speed]], [[hand (unit)|hands]] for heights of horses, etc.). 

{{em|Special considerations:}}
* Quantities set via definition (as opposed to measured quantities) should be given first in the units used in the definition, even if this makes the structure of presentation inconsistent: {{xt|During metrification, the speed limit was changed from 30{{nbsp}}mph (48{{nbsp}}km/h) to 50{{nbsp}}km/h (31{{nbsp}}mph)}}.
** Or use ''about'' to emphasize which is the statutory, exact value: {{xt|...from 30{{nbsp}}mph (about 48{{nbsp}}km/h) to 50{{nbsp}}km/h (about 31{{nbsp}}mph)}}.
* Nominal quantities (e.g. {{xt|2{{nbsp}}×{{nbsp}}4}} [[Lumber#North American softwoods|lumber]]) require consideration of whether the article is concerned with the item's actual dimensions or merely with its function. In some cases, the nominal quantity may suffice; in others it may be necessary to give the nominal size (often in non-SI units), the actual size in non-SI units, and the actual size in SI units.
* Whenever a conversion is given, the converted quantity's value should match the precision of the source {{crossref|(see {{section link||Unit conversions}})}}.
* Where the article's primary units differ from the units given in the source, the {{tlx|convert}} template's <code>|order=flip</code> flag can be used; this causes the {{em|original}} unit to be shown as secondary in the article, and the {{em|converted}} unit to be shown as primary: <code><nowiki>{{convert|200|mi|km|order=flip}}</nowiki></code> &rarr; {{xt|The two cities are {{convert|200|mi|km|order=flip}} apart.}}

===Unit conversions===

{{shortcut|MOS:CONVERSIONS|WP:MOSCONVERSIONS}}

Where English-speaking countries use different units for the same quantity, provide a conversion in parentheses: {{xt|the Mississippi River is {{convert|2320|mi|km|0}} long}}; {{xt|the Murray River is {{convert|2508|km|mi|0}} long}}. But in science-related articles, supplying such conversion is not required unless there is some special reason to do so.
* Where an [[imperial unit]] is not part of the [[United States customary units|US customary system]], or vice versa{{snd}}and in particular, where those systems give a single term different definitions{{snd}}a double conversion may be appropriate: {{xt|Rosie weighed {{convert|80|kg|lb stlb}}}} (markup: <code><nowiki>{{convert|80|kg|lb stlb}}</nowiki></code>); {{xt|{{nobr|The car}} had a fuel economy of {{convert|5|L/100km|mpgus mpgimp|abbr=on}}}} (markup: <code><nowiki>{{convert|5|L/100km|mpgus mpgimp|abbr=on}}</nowiki></code>).
* Generally, conversions to and from metric units and US or imperial units should be provided, except:
** When inserting a conversion would make a common or linked expression awkward ({{xt|The four-minute mile}}).
** In some topic areas (for example maritime subjects where nautical miles are the primary units, or American football where [[yard (unit)|yards]] are primary) it can be excessive to provide a conversion for every quantity. In such cases consider noting that the article will use a particular unit{{snd}}possibly giving the conversion factor to other, familiar units in a parenthetical note or a footnote{{snd}}and link the first occurrence of each unit but not give a conversion every time it occurs. Applying this principle may require editorial discretion; for example, in scientific articles the expected level of reader sophistication should be taken into account.  <!-- At https://en.wikipedia.org/wiki/Wikipedia_talk:Manual_of_Style/Dates_and_numbers/Archive_155#Unit_conversions_in_science_articles  there's a very long and detailed discussion about this point which kind of pooped out and might be worth reviving-->
* Converted quantity values should use a {{em|level of precision}} similar to that of the source quantity value, so {{xt|the Moon is 380,000{{nbsp}}kilometres (240,000{{nbsp}}mi) from Earth}}, not {{!xt|(236,121{{nbsp}}mi)}}. Small numbers, especially if approximate, may need to be converted to a range where rounding would cause a significant distortion, so {{xt|about one mile (1–2{{nbsp}}km)}}, not {{!xt|about one mile (2{{nbsp}}km)}}. Be careful especially when your source has already converted from the units you're now converting back to. This may be evidenced by multiples of common conversion factors in the data, such as 160 km (from 100 miles). {{crossref|See [[false precision]].}}
* {{tlx|convert}} (and other [[:Category:Conversion templates|'''conversion templates''']]) can be used to convert and format many common units.
* In a '''direct quotation''', always retain the source units. Any conversions can be supplied either in the quote itself (in square brackets, following the original measurement) or in a footnote. {{crossref|See [[Wikipedia:Footnotes|footnoting]] and [[Wikipedia:Citing sources|citing sources]].}}
* {{tlx|Units attention}} may be added to articles needing general attention regarding choice of units and unit conversions.

===Unit names and symbols===

{{shortcut|MOS:UNITNAMES|MOS:UNITSYMBOLS|WP:UNITNAMES|WP:UNITSYMBOLS}}
:{{em|Definitions:}}
:* Examples of '''unit names''': foot, metre, kilometre, (''US:'' meter, kilometer).
:* Examples of '''unit symbols''': ft, m, km.
* Unit names and symbols should follow the practice of reliable sources.
* In prose, unit names should be given in full if used only a few times, but symbols may be used when a unit (especially one with a long name) is used repeatedly, after spelling out the first use (e.g. {{xt|Up to 15 kilograms of filler is used for a batch of 250{{nbsp}}kg}}).
** Exception: Certain units<!--<<perhaps identify these in table of specific units elsewhere on this page--> are generally represented by their symbols (e.g. {{xt|&deg;C}} rather than {{!xt|degrees Celsius}}) even on first use, though their unit names may be used for emphasis or clarity ({{xt|conversion of degrees Celsius to degrees Fahrenheit}}).
** Exception: Consider using ''inches'' (but not ''in.'') in place of ''in'' where the latter might be misread as a preposition<!--can someone supply an example? (if no one can think of one after a while, then maybe this exception never actually arises)-->{{mdashb}}but not where the value is followed by a parenthesized conversion e.g. {{xt|bolts 5&nbsp;in (12.7&nbsp;cm) long}}, or is part of such a conversion ({{xt|bolts 12.7&nbsp;cm (5&nbsp;in) long}}).
* Where space is limited, such as in tables, infoboxes, parenthetical notes, and mathematical formulas, unit symbols are preferred.
* Units unfamiliar to general readers should be presented as a name{{ndash}}symbol pair on first use, linking the unit name ({{xt|Energies rose from 2.3 [[megaelectronvolt]]s (MeV) to 6{{nbsp}}MeV}}).
* Ranges use unspaced en dash ({{tlx|ndash}}) if only one unit symbol is used at the end (e.g. {{xt|5.9{{ndash}}6.3{{nbsp}}kg}}), and spaced en dash ({{tlx|snd}}) if two symbols are used (e.g. {{xt|3{{nbsp}}μm{{snd}}1{{nbsp}}mm}}); ranges in prose may be specified using either unit symbol or unit names, and units may be stated either after both numerical values or after the last (all acceptable: {{nobr|{{xt|from 5.9 to 6.3 kilograms}}}}; {{nobr|{{xt|from 5.9 kilograms to 6.3 kilograms}}}}; {{nobr|{{xt|from 5.9 to 6.3{{nbsp}}kg}}}}; {{nobr|{{xt|from 5.9{{nbsp}}kg to 6.3{{nbsp}}kg}}}}).
* Length{{ndash}}width, length{{ndash}}width{{ndash}}height and similar dimensions may be separated by the multiplication sign (<code>×</code> or <code>&amp;times;</code>) or the word <code>by</code>.
** The {{xtn|×}} symbol is preceded by a space (preferably non-breaking), and followed by a space (which may also be non-breaking in short constructions), and  each number should be followed by a unit name or symbol:
*** {{xt|1 m × 3 m × 6 m}}, not {{nobr| {{!xt|1 × 3 × 6 m}}}}, {{!xt|(1 × 3 × 6) m}}, nor {{nobr| {{!xt|1 × 3 × 6 m<sup>3</sup>}} }}
*** {{xt|a metal plate 1 ft × 3 ft × 0.25 in}}
*** {{xt|a railroad easement 10 ft × 2.5 mi}}
** With {{xtn|by}}, the unit need be given only once if it is the same for all dimensions: {{nobr| {{xt|1 by 3 by 6 metres}} }} or {{nobr| {{xt|1 by 3 by 6 m}} }}
** The unspaced letter {{xt|x}} may be used in common terms such as {{xt|[[4x4]]}}.

{| class="wikitable"
|+ {{vanchor|General guidelines on use of units}}
|-
! {{Vert header|<small>Aspect</small>}}
! Guideline<!--this column picks up whatever width is left over from other columns-->
! style="width:40px;"<!--undersized width specification means column size is set by widest word/nobreaked phrase in column contents-->| [[File:Yes check.svg|11px|link=|alt=]] Acceptable
! style="width:40px;"<!--undersized width specification means column size is set by widest word/nobreaked phrase in column contents-->|[[File:X mark.svg|11px|link=|alt=]] Unacceptable
|-
|rowspan=8 {{Vert header|va=middle|<small>'''Unit names and symbols'''</small>}}
|Except as listed in the {{section link||Specific units}} table below, unit {{em|symbols}} are uncapi{{shy}}tal{{shy}}ized unless they are derived from a proper name, in which case the first letter (of the base unit symbol, not of any prefix) is capitalized.{{efn|1=These definitions are consistent with all units of measure mentioned in the ''SI Brochure''<ref name="SI Brochure" /> and with all units of measure catalogued in [[European units of measurement directives|EU directive 80/181/EEC]].<ref>{{cite web |title=Council Directive of 20 December 1979 on the approximation of the laws of the Member States relating to units of measurement |id=80/181/EEC (Document 01980L0181-20090527) |work=Eur-Lex.Europa.eu |publisher=[[European Union]] |date=2017 |orig-year=1979 |url=http://eur-lex.europa.eu/legal-content/EN/TXT/?qid=1397640809938&uri=CELEX:01980L0181-20090527 |access-date=December 12, 2017}}</ref>}}
| {{ xt|8 kg}}<br />{{ xt|100 kPa}}
| {{!xt|8 Kg}}<br />{{!xt|100 kpa}}
|-
|Unit symbols are undotted.
|{{ xt|38 cm of rope }}
|{{!xt|38 cm<big>.</big> of rope}}
|-
|rowspan=2 | Unit {{em|names}} are given in lower case except: where any word would be capital{{shy}}ized, or where otherwise specified in the SI brochure<ref name="SI Brochure">{{cite book |title=SI Brochure: The International System of Units (SI) |edition=9th |year=2019 |publisher=[[Bureau International des Poids et Mesures]] |url=https://www.bipm.org/utils/common/pdf/si-brochure/SI-Brochure-9-EN.pdf |section=Chapter 4: Non-SI units that are accepted for use with the SI |access-date=2020-09-24}} Table 8, p 145, gives additional guidance on non-SI units.</ref> or this Manual of Style.
|{{plainlist|
* {{ xt|A gallon is 4{{nbsp}}quarts.}}
* {{ xt|4 pascals}}
}}
|{{plainlist|
* {{!xt|A Gallon is 4{{nbsp}}Quarts.}}
* {{!xt|4 Pascals}}
}}
|-
|{{plainlist|
* {{ xt|He walked several miles.}}
* {{ xt|Miles of trenches were dug.}}
}}
|
|-
|The spelling of certain unit names (some of which are listed in {{section link||Specific units}}, below) varies with the [[Wikipedia:Manual of Style#National varieties of English|variety of English followed by the article]].
|
|
|-
|rowspan=2 | Write unit names and symbols in upright ([[Roman type|{{sic|hide=y|roman}}]]) type, except where emphasizing in context.
| {{ xt|10{{nbsp}}m}}<br />{{ xt|29 kilograms}}
| {{!xt|10{{nbsp}}{{em|m}}}}<br />{{!xt|29 {{em|kilograms}}}}
|-
| {{ xt|Thus each two-liter jug contained only two {{em|quarts}}.}}
|
|-
|Do not use precomposed unit symbol characters.
|
|{{!xt|㎓, ㎦, ㎍, ㎖, ㎉}}
|-
|rowspan=7 {{Vert header|va=middle|<small>'''Numeric values'''</small>}}<!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES-->
|Do not spell out numbers before unit {{em|symbols}}{{nbsp}}...
|{{ xt|12{{nbsp}}min}}
|{{!xt|twelve{{nbsp}}min}}
|-
|...{{nbsp}}but words {{em|or}} figures may be used with unit {{em|names}}.
|{{plainlist|
* {{ xt|twelve minutes}}
* {{ xt|12 minutes}}
}}
|
|-
| Use a non-breaking space ({{tlx|nbsp}} or <code>&amp;nbsp;</code>) between a number and a unit {{em|symbol}}, or use {{tlx|nowrap}}{{nbsp}}...
| {{xt|29{{nbsp}}kg}} {{nowr|(markup: <code>29&amp;nbsp;kg</code>}} or {{nowr|<code><nowiki>{{nowrap|29 kg}}</nowiki></code>)}}
| style="vertical-align: top"| {{!xt|29kg}}
|-
| ... though with certain symbols ''no'' space is used (see "Specific{{nbsp}}units" table below){{nbsp}}...
| {{nobr|{{xt|23&deg;}} {{xt|47&prime;}} {{xt|22&Prime;}} }}
| {{nobr|{{!xt|23{{nbsp}}&deg;}} {{!xt|47{{nbsp}}&prime;}} {{!xt|22{{nbsp}}&Prime;}} }}
|-
| ... and a normal space is used between a number and a unit {{em|name}}.
| {{xt|29{{nbsp}}kilograms}}<br />(markup: <code>29&nbsp;kilograms</code>)
|
|-
|To form a value and a unit {{em|name}} into a compound adjective use a hyphen or hyphens{{nbsp}}...
|{{plainlist|
* {{ xt|a five-day holiday}}
* {{ xt|a five-cubic-foot box}}
* {{ xt|a 10-centimeter blade}}
}}
|
|-
|... but a non-breaking space (never hyphen) separates a value and unit {{em|symbol}}.
|{{plainlist|
* {{ xt|a blade 10 cm long}}<!--What about "a 10 cm bridge"?-->
}}
| {{!xt|a 10-cm blade}}
|-
|rowspan=5 {{Vert header|va=middle|<small>'''Plurals'''</small>}}<!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES-->
|[[International System of Units|SI]] unit {{em|names}} are pluralized by adding the appropriate {{xt|-s}} or {{xt|-es}} suffix{{nbsp}}...<!--Not that it matters much, but I'm having trouble finding an SI unit taking -es. -->
|{{ xt|1 ohm}}; {{xt|10 ohms}}<!--What's an example with "-es"?-->
|
|-
| ... except for these irregular forms.
| {{ xt|1 henry}}; {{ xt|10 henries}}<br />{{ xt|1 hertz}}; {{ xt|10 hertz}}<br />{{ xt|1 lux}}; {{xt|10 lux}}<br />{{ xt|1 siemens}}; {{xt|10 siemens}}
|{{!xt|10 henrys }}<br />{{!xt|10 hertzes}}<br />{{!xt|10 luxes}}<br />{{!xt|10 siemenses}}
|-
|rowspan=2 | Some non-SI units have irregular plurals.<!--This is meant to be placeholder which perhaps someone can expand (though foot, feet is the only example I can think of at the moment).--><!--Pedal, peddle (more, meet; group, greet; trump, tweet) ... mouth, momentous ... are we there yet ...-->
| {{ xt|1 foot}}; {{xt|10 feet}}
| {{!xt|10 foots}}
|-
| {{ xt|1 stratum}}; {{nobr|{{xt|10 strata}} (unusual)}} <!--Rare, but is occasionally used as a measurement unit; can't think of any others, didn't find any in searching.-->
| {{!xt|10 stratums}}
|-
|Unit {{em|symbols}} (in any system) are identical in singular and plural.
|{{plainlist|
* {{nobr|{{xt|grew from 1 in to 2 in}} }}
* {{nobr|{{xt|grew from 1 inch to 2 inches}} }}
* {{nobr|{{xt|grew from one to two inches}} }}
}}
|{{nobr|{{!xt|grew from 1 in to 2 ins}} }}
|-
|rowspan=5 {{Vert header|va=middle|<small>'''Powers'''</small>}}<!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES-->
|Format exponents using <nowiki><sup></nowiki>, not special characters.
|{{xt|km<sup>2</sup>}}<br />{{nobr|(markup: <code>km&lt;sup>2&lt;/sup></code>)}}
|{{!xt|km&#178;}}<br />(<code>km&amp;#178;</code>)
|-
|Or use {{xtn|squared}} or {{xtn|cubed}} ({{em|after}} the unit being modified).
|rowspan=2|{{xt|ten metres per second squared}}
|{{!xt|ten metres per squared second}}
|-
|rowspan=2| For areas or volumes only, {{xtn|square}} or {{xtn|cubic}} may be used ({{em|before}} the unit being modified).
|{{!xt|ten metres per square second}}
|-
|{{xt|tons per square mile}}
|
|-
| {{xtn|sq}} or {{xtn|cu}} may be used with US customary or imperial units, but not with [[International System of Units|SI]] units.
| {{ xt|15{{nbsp}}sq{{nbsp}}mi}}<br />{{ xt|3{{nbsp}}cu{{nbsp}}ft }}
| {{!xt|15{{nbsp}}sq{{nbsp}}km}}<br />{{!xt|3{{nbsp}}cu{{nbsp}}m }}
|-
|rowspan=4 {{Vert header|va=middle|<small>'''Products'''</small>}}<!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES-->
|Indicate a product of unit {{em|names}} with either a hyphen or a space.
|{{plainlist|
* {{ xt|foot-pound}}
* {{ xt|foot pound}}
}}
|{{plainlist|
* {{!xt|footpound}}
* {{!xt|foot&sdot;pound}}
}}
|-
|Indicate a product of unit {{em|symbols}} with <code>&amp;[[dot operator|sdot]];</code> or <code>&amp;[[non-breaking space|nbsp]];</code>.
|{{plainlist|1= <!-- 1= is needed because text below contains = -->
* {{ xt|ms}} = millisecond
* {{ xt|m&sdot;s}} or {{xt|m{{nbsp}}s}} = metre-second
}}
|
|-
|{{em|Exception:}} In some topic areas, such as power engineer{{shy}}ing, certain products take neither space nor <code>&amp;sdot;</code>. Follow the practice of reliable sources in the article's topic area.
|{{plainlist|
* [[watt hour|{{xt|Wh}}]], [[volt ampere|{{xt|VA}}]], [[ampere hour|{{xt|Ah}}]]
* {{xt|kWh}}, {{xt|MVA}}, {{xt|GAh}}
}}
|
|-
|To pluralize a product of unit {{em|names}}, pluralize only the final unit. (Unit {{em|symbols}} are never pluralized.)
|{{ xt|ten foot-pounds}}
|{{!xt|ten feet-pounds}}
|-
|rowspan=7 {{Vert header|va=middle|<small>'''Ratios, rates, densities'''</small>}}<!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES-->
|Indicate a ratio of unit {{em|names}} with {{xtn|per}}.
|{{ xt|meter per second}}
|{{!xt|meter/second}}
|-
|rowspan=2|Indicate a ratio of unit {{em|symbols}} with a forward slash (<code>/</code>), followed by either a single symbol or a parenthesized product of symbols{{snd}}do not use multiple slashes. Or use{{nbsp}}<sup>&minus;1</sup>,{{nbsp}}<sup>&minus;2</sup>, etc.
|{{plainlist|
* {{ xt|metre per second}}
* {{ xt|m/s}}
* {{ xt|m&sdot;s<sup>&minus;1</sup>}}
}}
|{{plainlist|
* {{!xt|mps}}
}}
|-
|{{plainlist|
* {{ xt|kg/(m&sdot;s)}}
* {{ xt|kg&sdot;m<sup>&minus;1</sup>&sdot;s<sup>&minus;1</sup>}}
}}
|{{plainlist|
* {{!xt|kg/m&sdot;s}}
* {{!xt|kg/m/s}}
}}
|-
|To pluralize a ratio of unit {{em|names}}, pluralize only the numerator unit. (Unit {{em|symbols}} are never pluralized.)
|{{plainlist|
* {{nowrap|{{xt|ten newton-metres per second}} }}<!--Nowrap on longest value in column establishes minimum col width.-->
* {{xt|10 N&sdot;m/s}}
}}
|
|-
|Some of the special forms used in the imperial and US customary systems are shown here{{nbsp}}...
|{{plainlist|1= <!--1= is needed because text below contains =-->
* {{ xt|mph}} = miles per hour
* {{ xt|mpg}} = miles per gallon
* {{ xt|psi}} = [[pound (force)|pounds]] per square inch
}}
|
|-
|rowspan=2| ... but only the slash or negative exponent notations are used with SI (and other metric) units.
| {{plainlist|
* {{ xt|g/m<sup>2</sup>}}
* {{ xt|g&sdot;m<sup>&minus;2</sup>}}
}}
| {{!xt|gsm}}
|-
| {{plainlist|
* {{ xt|km/h}}
* {{ xt|km&sdot;h<sup>&minus;1</sup>}}
}}
| {{!xt|kph}}
|-
|rowspan=4 {{Vert header|va=middle|<small>'''Prefixes'''</small>}}<!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES-->
|Prefixes should not be separated by a space or hyphen.
|{{ xt|kilopascal}}
|{{plainlist|
* {{!xt|kilo pascal}}
* {{!xt|kilo-pascal}}
}}
|-
| Prefixes are added without contraction,<!--give example--> except as shown here:
| {{ xt|kilohm }}<br />{{ xt|megohm }}<br />{{xt|hectare}}
| {{!xt|kiloohm}}<br />{{!xt|megaohm}}<br />{{!xt|hectoare}}
|-
|The {{xtn|deci-}}, {{xtn|deca-}}, and {{xtn|hecto-}} prefixes should generally be avoided; exceptions include<!--Check SI source; also, since we're supposed to follow the units in sources, don't those control anyway?--> decibel, hectolitre, hectare, and hectopascal.
|{{plainlist|
* {{ xt|100 metres}}
* {{ xt|0.1 km}}
}}
|{{!xt|1 hectometre}}
|-
| Do not use [[wikt:M#Number|{{!xt|M}}]] for 10<sup>3</sup>, {{!xt|MM}} for 10<sup>6</sup>, or {{!xt|B}} for 10<sup>9</sup> (except as noted elsewhere on this page for {{xtn|M}} and {{xtn|B}}, e.g. [[#Currencies and monetary values|for monetary values]])
| {{ xt|3 km }}<br />{{ xt|8 MW }}<br />{{ xt|125 GeV}}
| {{!xt|3 Mm }}<br />{{!xt|8 MMW }}<br />{{!xt|125 BeV}}
|-
|rowspan=4 {{Vert header|va=middle|<small>'''Mixed units'''</small>}}<!--← Use <br /> to make this column as narrow as possible.--><!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES-->
|rowspan=2| Mixed units are traditionally used with the imperial and US customary systems{{nbsp}}...
|{{anchor|Mixed units}}<!--← This anchor should go at the portion of the row which is vertically highest.-->{{plainlist|
* {{xt|a wall 1 ft 1 in thick}}
* {{xt|a wall 1 foot 1 inch thick }}
* {{xt|a man 6 feet 2 inches tall}}
* {{xt|a 6-foot 2-inch man}}
* {{xt|a 6 ft 2 in man}}
}}
|{{plainlist|
* {{nobr| {{!xt|1 ft{{hsp}}, 1 in }} (no comma) }}
* {{!xt|1 foot{{hsp}}, 1 inch}}
* {{!xt|a man 6 foot 2 tall}}
* {{!xt|a 6-foot 2 man}}
* {{nbsp}}
}}
|-
|{{plainlist|
* {{xt|1 US fl pt 8 oz}}
* {{xt|1 US fl pt 8 US fl oz}}
}}
|
|-
|... and in expressing time durations{{nbsp}}...
|{{plainlist|
* {{xt|1:30:07}}
* {{xt|1:30}}{{thinsp}}<ref group="note">Use this format only where it is clear from context whether it means hours and minutes (H:MM) or minutes and seconds (M:SS).</ref>
* {{xt|{{nobr|1 h 30 min 7 s}}}}
* {{xt|{{nobr|01<sup>h</sup> 30<sup>m</sup> 07<sup>s</sup>}}}}{{thinsp}}{{refn|group=note|This format is used in astronomy (see the IAU Style Manual<ref>{{cite book |title=IAU Style Manual |first=G. A. |last=Wilkins |chapter=5.14 Time and angle |page=S23 |date=1989 |url= https://www.iau.org/static/publications/stylemanual1989.pdf |format=PDF |publisher=[[International Astronomical Union]] |access-date=12 December 2017}}</ref> for details).}}
}}
||{{plainlist|
* {{!xt|{{nobr|1:30&prime;07&Prime;}}}}
* {{!xt|{{nobr|1:30&prime;}}}}
* {{!xt|{{nobr|1 hr 30 min 7 sec}}}}
* {{!xt|{{nobr|1 h 30 m 7 s}}}}
}}
|-
|... but are not used with metric units.
|{{plainlist|
* {{xt|1.33 m }}
* {{xt|133 cm }}
}}
|{{!xt|1 m 33 cm}}
|}
{{em|Note to table:}}
{{reflist | group=note}}

===Specific units===

* The following table lists only units that need special attention.
* The ''SI Brochure''<ref name="SI Brochure" /> should be consulted for guidance on use of other SI and non-SI units.

{|class="wikitable"
|+ Guidelines on specific units
|-
! {{Vert header|<small>Group</small>}}
! style="width:40px;"<!--undersized width specification means column size is set by widest word/nobreaked phrase in column contents-->| Name
! style="width:40px;"<!--undersized width specification means column size is set by widest word/nobreaked phrase in column contents-->| Symbol
! Comment<!--this column picks up whatever width is left over from other columns-->
|-
| rowspan = 8 {{Vert header|va=middle|<small>'''Length, speed'''</small>}}<!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS-->
| {{plainlist|
* inch
* foot
}}
| {{plainlist|
* {{ xt|in}}
* {{ xt|ft}}
}}
| Do not use <code>&amp;prime;</code>{{nbsp}}({{!xt|&prime;}}), <code>&amp;Prime;</code>{{nbsp}}({{!xt|&Prime;}}), apostrophe{{nbsp}}({{!xt|'}}), or quote{{nbsp}}({{!xt|"}}).
|-
| foot per second
| {{xt|ft/s}} ({{em|not}} {{!xt|[[Frames per second|fps]]}})
|
|-
| [[Hand (unit)|hand]]
| {{xt|h}} or {{xt|hh}}
| Equal to 4 inches; used in measurement of horses. A dot may be followed by additional inches e.g. {{nobr|{{xt|16.2 hh}}}} indicates {{nobr|16 hands 2 inches.}}
|-
|{{plainlist|
* [[Knot (unit)|knot]]
* {{nobr|knot [[indicated airspeed]]}}
* {{nobr|knot [[calibrated airspeed]]}}
* {{nobr|knot [[equivalent airspeed]]}}
* {{nobr|knot [[true airspeed]]}}
* {{nobr|knot [[groundspeed]]}}
}}
|{{plainlist|
* {{nobr|{{xt|kn}} {{nobr|({{em|not}} {{!xt|[[kilotonne|kt]]}}, {{!xt|[[Karat|Kt]]}}, or {{!xt|[[kilonewton|kN]]}})}}}}
* {{nobr|{{xt|KIAS}} or {{xt|kn}}}}
* {{xt|KCAS}}
* {{xt|KEAS}}
* {{xt|KTAS}}
* {{nobr|{{xt|kn}} {{nobr|({{em|not}} {{!xt|KGS}})}}}}
}}
| Used in aviation contexts for aircraft and wind speeds, and also used in some nautical and general meteorological contexts. When applied to aircraft speeds, {{xt|kn}} means {{xt|KIAS}} unless stated otherwise; if {{xt|kn}} is used for calibrated airspeed, equivalent airspeed, true airspeed, or groundspeed, explicitly state and link to, upon first use, the type of speed being referred to (for instance, {{xt|kn [[equivalent airspeed]]}}, or, if severely short of space, {{xt|kn [[Equivalent airspeed|EAS]]}}); for airspeeds other than indicated airspeed, the use of the specific abbreviation for the type of airspeed being referred to (such as {{xt|KEAS}}) is preferred. When referring to indicated airspeed, either {{xt|kn}} or {{xt|KIAS}} is permissible. Groundspeeds and wind speeds ''must'' use the abbreviation {{xt|kn}} only.
|-
| {{plainlist|
* metre
* meter {{em|(US)}}
}}
| {{xt|m}}
|
|-
| micron
| {{xt|&mu;m}} ({{em|not}} {{!xt|&mu;}})
| Markup: <code>&amp;mu;m</code>{{nbsp}} Link to [[micrometre]] (for which micron is a synonym) on first use.
|-
| [[astronomical unit]]
| {{xt|au}}<br />{{nobr| ({{em|not}} {{!xt|A.U.}}, {{!xt|ua}}) }}
| The preferred option is {{xt|au}}. Articles that already use {{xtn|AU}} may switch to au or continue with AU; seek consensus on the talk page.
|-
|{{plainlist|
* mile
* miles per hour
* nautical mile
}}
|{{plainlist|
* {{xt|mi}}
* {{xt|mph}}<!--not ever mi/h??-->
* {{nobr| {{xt|nmi}} or {{xt|NM}} {{nobr|({{em|not}} {{!xt|[[nanometre|nm]]}} or {{!xt|M}})}} }}
}}
| In nautical and aeronautical contexts where there is risk of confusion with nautical miles, consider writing out references to [[statute mile]]s as e.g. {{xt|5{{nbsp}}statute{{nbsp}}miles}} rather than simply {{!xt|5{{nbsp}}miles}}.
|-
| rowspan = 7 {{Vert header|va=middle|<small>'''Volume, flow'''</small>}}<!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS-->
| rowspan = 2 | {{plainlist|
* cubic centimetre
* {{nobr| cubic centimeter {{em|(US)}} }}
}}
| {{xt|cm<sup>3</sup>}}
| Markup: <code><nowiki>cm<sup>3</sup></nowiki></code>
|-
| {{xt|cc}}
| Non-SI abbreviation used for certain [[engine displacement]]s. Link to [[Cubic centimetre]] on first use.<!--I wonder if this can't be better coordinated with mpg, mph, etc. in earlier table.-->
|-
|{{plainlist|
* imperial fluid ounce
* imperial pint
* imperial quart
* imperial gallon
* US fluid ounce
* US dry pint
* US liquid pint
* US dry quart
* US liquid quart
* US gallon
}}
|{{plainlist|
* {{xt|imp fl oz}}
* {{xt|imp pt}}
* {{xt|imp qt}}
* {{xt|imp gal}}
* {{xt|US fl oz}} 
* {{xt|US dry pt}}
* {{xt|US liq pt}}
* {{xt|US dry qt}}
* {{xt|US liq qt}}
* {{xt|US gal}}
}}
|
*{{xtn|US}} or {{xtn|imperial}} (or {{xtn|imp}}) must be specified for all these units.
*{{xtn|fluid}} or {{xtn|fl}} must be specified for fluid ounces (to avoid ambiguity versus [[avoirdupois ounce]] and [[troy ounce]]).
*For US pints and quarts, {{xtn|dry}} or {{xtn|liquid (liq)}} are needed to be fully unambiguous, though context may determine whether or not to repeat those qualifiers on every use in a given article.
|-
| cubic foot
| {{xt|cu ft}} ({{em|not}} {{!xt|cf}})
| Write {{xt|five million cubic feet}}, {{xt|5,000,000{{nbsp}}cu{{nbsp}}ft}}, or {{xt|{{val|5|e=6|u=cuft}}}}, not {{!xt|5{{nbsp}}MCF}}.
|-
| {{nobr| cubic foot per second }}
| {{xt|cu ft/s}} ({{em|not}} {{!xt|cfs}})
|
|-
| {{plainlist|
* litre
* liter {{em|(US)}}
}}
| {{nobr|{{xt|L}} {{nobr|({{em|not}} {{!xt|l}} or {{!xt|ℓ}})}}}}
| The symbol l (lowercase "el") in isolation (i.e. outside forms as ml) is easily mistaken for the digit{{nbsp}}1 or the capital {{nobr|letter I ("eye")}} and should not be used.
|-
| {{plainlist|
* millilitre
* milliliter {{em|(US)}}
}}
| {{xt|ml}} or {{xt|mL}}
| Derivative units of the litre may use l (lowercase "el") as guided by [[WP:ENGVAR]].
|-
| rowspan=7 {{Vert header|va=middle|<small>'''Mass, weight, force, density, pressure'''</small>}}<!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS-->
|{{plainlist|
* gram
* kilogram
}}
|{{plainlist|
* {{xt|g}}
* {{xt|kg}}
}}
| Not {{!xt|gramme}}, {{!xt|kilogramme}}
|-
|{{plainlist|
* [[long ton]]
* [[short ton]]
}}
|{{plainlist|
* {{xt|long ton}}
* {{xt|short ton}}
}}
| Spell out in full.
|-
| {{plainlist|
* [[tonne]]
* [[tonne|metric ton]] {{em|(US)}}
}}
| {{xt|t}} {{nobr|({{em|not}} {{!xt|mt}}, {{!xt|MT}}, or {{!xt|[[Megatonne|Mt]]}})}}
|
|-
| {{nobr| pound per square inch }}
| {{xt|psi}}
|
|-
|{{plainlist|
*troy ounce
*troy pound
}}
|{{plainlist|
*{{xt|oz t}}
*{{xt|lb t}}
}}
|rowspan=2| the qualifier {{xtn|t}} or {{xtn|troy}} must be specified where applicable. Use the qualifier avdp ([[avoirdupois]]) only where there is risk of confusion with troy ounce, imperial fluid ounce, US fluid ounce, or troy pound; but articles about precious metals, black powder, and gemstones<!--Is this list complete?--> should always specify which type of ounce (avoirdupois or [[Troy weight|troy]]) is being used, noting that these materials are normally measured in troy ounces and grams.
|-
|{{plainlist|
*avoirdupois ounce
*avoirdupois pound
}}
|{{plainlist|
*{{xt|oz}} or {{xt|oz avdp}}
*{{xt|lb}} or {{xt|lb avdp}}
}}
|-
| [[Carat (mass)|carat]]
| {{xt|carat}}
| Used to express masses of gemstones and pearls.
|-
| {{Vert header|va=middle|<small>'''Purity'''</small>}}<!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS-->
| [[Carat (purity)|carat or karat]]
| {{nobr|{{xt|k}} or {{xt|Kt}} {{nobr|({{em|not}} {{!xt|[[Kilotonne|kt]]}} or {{!xt|[[Kelvin|K]]}})}}}}
| A measure of purity for gold alloys. (Do not confuse with the unit of mass with the same spelling.)
|-
| rowspan=3 {{Vert header|va=middle|<small>'''Time'''</small>}}
| {{plainlist|
* second
* minute
* hour
}}
| {{plainlist|
* {{xt|s}}
* {{xt|min}}
* {{xt|h}}
}}
|Do not use <code>&amp;prime;</code>{{nbsp}}({{!xt|&prime;}}), <code>&amp;Prime;</code>{{nbsp}}({{!xt|&Prime;}}), apostrophe{{nbsp}}({{!xt|'}}) or quote{{nbsp}}({{!xt|"}}) for minutes or seconds. See also the hours–minutes–seconds formats for time durations described in the [[#Mixed units|Unit names and symbols table]].
|-
| rowspan=2|year
| {{xt|a}}
| Use {{xtn|a}} only with an [[SI annus|SI prefix multiplier]] ({{xt|a rock formation 540{{nbsp}}Ma{{nbsp}}old}}, not {{!xt|Life expectancy rose to 60{{nbsp}}a}}).
|-
| {{xt|y}} or {{xt|yr}}
| {{crossref|See {{section link||Long periods of time}} for all affected units.}}
|-
| rowspan=4 <!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS-->{{Vert header|va=middle|<small>'''Information, data'''</small>}}
| bit
| {{xt|bit}} {{nobr|({{em|not}} {{!xt|b}} or {{!xt|B}})}}
| rowspan=4 | {{crossref|See also {{section link||Quantities of bytes and bits}}, below.}} Do not confuse bit/second or byte/second with [[baud|baud (Bd)]].
|-
| byte
| {{nobr| {{xt|B}} or {{xt|byte}} ({{em|not}} {{!xt|b}} or {{!xt|[[octet (computing)|o]]}}) }}
|-
| bit per second
| {{xt|bit/s}} ({{em|not}} {{!xt|bps}}, {{!xt|b/s}})
|-
| byte per second
| {{xt|B/s}} or {{xt|byte/s}} {{nobr|({{em|not}} {{!xt|Bps}}, {{!xt|bps}}, {{!xt|b/s}})}}
|-
| rowspan = 4 {{Vert header|va=middle|<small>'''Angle'''</small>}}<!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS-->
|-
| [[arcminute]]
| {{xt|&prime;}}
| Markup: <code>&amp;prime;</code>{{nbsp}} ([[prime (symbol)|prime&nbsp;&prime;]] not apostrophe/{{zwsp}}single quote{{nbsp}}{{!xt|'}}). {{nobr|No space ({{xt|47&prime;}}, not {{!xt|47{{nbsp}}&prime;}}). }}
|-
| [[arcsecond]]
| {{xt|&Prime;}}
| Markup: <code>&amp;Prime;</code>{{nbsp}} ([[double prime (symbol)|double prime&nbsp;&Prime;]] not double-quote{{nbsp}}{{!xt|"}}). {{nobr|No space ({{xt|22&Prime;}}, not {{!xt|22{{nbsp}}&Prime;}}). }}
|-
| degree
| {{xt|&deg;}}
| Markup: <code>&amp;deg;</code> (degree &deg; not [[masculine ordinal]] {{!xt|&#186;}} or [[ring (diacritic)|ring]]&nbsp;{{thinsp}}{{!xt|&#778;}}{{hsp}}<!--<<hsp is needed to prevent crash between ring and closing paren, at least on some browsers-->). {{nobr|No space ({{xt|23&deg;}}, not {{!xt|23{{nbsp}}&deg;}}). }}
|-
| rowspan = 4 {{Vert header|va=middle|<small>'''Temperature'''</small>}}<!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS-->
| degree Fahrenheit
| {{xt|&deg;F}} ({{em|not}} {{!xt|F}})
| rowspan = 3 | Markup: <code>&amp;deg;</code>. Use a non-breaking space: {{nobr|<code>12{{tl|nbsp}}&amp;deg;C</code>}}, not {{nobr|<s><code>12&amp;deg;C</code></s>}} nor {{nobr|<s><code>12&amp;deg;{{t|nbsp}}C</code></s> }} {{nobr|({{xt|12{{nbsp}}&deg;C}}, not {{!xt|12&deg;C}} nor {{!xt|12&deg;{{nbsp}}C}}). }} Do not use the [[precomposed character]]s {{unichar|2103|Degree Celsius}} and {{unichar|2109|Degree Fahrenheit}}.
|-
| degrees [[Rankine scale|Rankine]]
| {{xt|&deg;R}} ({{em|not}} {{!xt|R}})
|-
| degree Celsius {{nobr|({{em|not}} degree centigrade)}}
| {{xt|&deg;C}} ({{em|not}} {{!xt|C}})
|-
| [[kelvin]] {{nobr|({{em|not}} degree kelvin)}}
| {{xt|K}} ({{em|not}} {{!xt|&deg;K}})
| Use a non-breaking space: <code><nowiki>12{{nbsp}}K</nowiki></code> (use [[K|the normal latin letter K]], not {{unichar|212A|KELVIN SIGN}})
|-
| rowspan = 2 {{Vert header|va=middle|<small>'''Energy'''</small>}}<!--WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS-->
| {{plainlist|
* [[calorie]]
* small calorie
* gram calorie
}}
| {{xt|cal}}
| rowspan=2 | In certain subject areas, ''calorie'' is convention{{shy}}ally used alone; articles following this practice should specify on first use whether the use refers to the small calorie or to the kilocalorie (large calorie). Providing conversions to [[International System of Units|SI]] units (usually calories to joules or kilocalories to kilojoules) may also be useful. A kilocalorie ({{xt|kcal}}) is 1000 calories. A calorie (small calorie) is the amount of energy required to heat 1 gram of water by 1{{nbsp}}°C. A kilocalorie is also a kilogram calorie.
|-
| {{plainlist|
* [[kilocalorie]]
* large calorie
* kilogram calorie
* ({{em|not}} Calorie{{snd}}{{nobr|can be ambiguous)}}
}}
| {{xt|kcal}}
|}

====Quantities of bytes and bits <span id="Binary prefixes"></span>====

{{shortcut|WP:COMPUNITS}}

In quantities of [[bit (computing)|bits]] and [[byte]]s, the prefixes {{xtn|kilo-}} (symbol {{xtn|k}} or {{xtn|K}}), {{xtn|mega-}} ({{xtn|M}}), {{xtn|giga-}} ({{xtn|G}}), {{xtn|tera-}} ({{xtn|T}}), etc., are ambiguous in general usage. The meaning may be based on a decimal system (like the standard [[International System of Units|SI]] prefixes), meaning 10<sup>3</sup>, 10<sup>6</sup>, 10<sup>9</sup>, 10<sup>12</sup>, etc., or it may be based on a binary system, meaning 2<sup>10</sup>, 2<sup>20</sup>, 2<sup>30</sup>, 2<sup>40</sup>, etc. The binary meanings are more commonly used in relation to solid-state memory (such as [[Random-access memory|RAM]]), while the decimal meanings are more common for data transmission rates, disk storage and in theoretical calculations in modern academic textbooks.
{{Bit and byte prefixes}}
Follow these recommendations when using these prefixes in Wikipedia articles:
* Following the SI standard, a lower-case {{xt|k}} should be used for "kilo-" whenever it means 1000 in computing contexts, whereas a capital {{xt|K}} should be used instead to indicate the binary prefix for 1024 according to JEDEC. If, under the exceptions detailed further below, the article otherwise uses IEC prefixes for binary units, use {{xt|Ki}} instead.
* Do not assume that the binary or decimal meaning of prefixes will be obvious to everyone. Explicitly specify the meaning of k and K as well as the primary meaning of M, G, T, etc. in an article ({{tlx|BDprefix}} is a convenient helper). Consistency within each article is desirable, but the need for consistency may be balanced with other considerations.
* The definition most relevant to the article should be chosen as primary for that article, e.g. specify a binary definition in an article on RAM, decimal definition in an article on [[hard drives]], [[bit rate]]s, and a binary definition for Windows file sizes, despite files usually being stored on hard drives.
* Where consistency is not possible, specify wherever there is a deviation from the primary definition.
* Disambiguation should be shown in bytes or bits, with clear indication of whether in binary or decimal base. There is no preference in the way to indicate the number of bytes and bits, but the notation style should be consistent within an article. Acceptable examples include:
** {{xt|A 64{{nbsp}}MB ({{nowrap|64{{nbsp}}×{{nbsp}}1024<sup>2</sup>-byte)}} video card and a 100{{nbsp}}GB {{nowrap|(100{{nbsp}}×{{nbsp}}1000<sup>3</sup>-byte)}} hard drive}}
** {{xt|A 64{{nbsp}}MB ({{nowrap|64{{nbsp}}×{{nbsp}}2<sup>20</sup>-byte)}} video card and a 100{{nbsp}}GB {{nowrap|(100{{nbsp}}×{{nbsp}}10<sup>9</sup>-byte)}} hard drive}}
** {{xt|A 64{{nbsp}}MB {{nowrap|(67,108,864-byte)}} video card and a 100{{nbsp}}GB {{nowrap|(100,000,000,000-byte)}} hard drive}}
* Avoid combinations with inconsistent form such as {{!xt|A 64{{nbsp}}MB {{nowrap|(67,108,864-byte)}} video card and a 100{{nbsp}}GB {{nowrap|(100{{nbsp}}×{{nbsp}}1000<sup>3</sup>-byte)}} hard drive}}. Footnotes, such as those seen in [//en.wikipedia.org/w/index.php?title=Power_Macintosh_5500&oldid=218088888 {{nowrap|Power Macintosh 5500}}], may be used for disambiguation.
* Unless explicitly stated otherwise, one byte is eight bits {{crossref|(see {{section link|Byte|History}})}}.

The [[IEC prefix]]es {{xtn|kibi-}} (symbol {{xtn|Ki}}), {{xtn|mebi-}} ({{xtn|Mi}}), {{xtn|gibi-}} ({{xtn|Gi}}), etc., are generally not to be used except:{{efn|1=Wikipedia follows common practice regarding [[byte]]s and other data traditionally quantified using [[binary prefix]]es (e.g. {{xtn|mega-}} and {{xtn|kilo-}}, meaning 2<sup>20</sup> and 2<sup>10</sup> respectively) and their unit symbols (e.g. {{xtn|MB}} and {{xtn|KB}}) for RAM and [[decimal prefix]]es for most other uses. Despite the IEC's 1998 international standard creating several new binary prefixes (e.g. mebi-, kibi-, etc.) to distinguish the meaning of the decimal [[SI prefix]]es (e.g. {{xtn|mega-}} and {{xtn|kilo-}}, meaning 10<sup>6</sup> and 10<sup>3</sup> respectively) from the binary ones, and the subsequent incorporation of these IEC prefixes into the [[IEC 80000-13|ISO/IEC 80000]], consensus on Wikipedia in computing-related contexts favours the retention of the more familiar but ambiguous units {{xtn|KB}}, {{xtn|MB}}, {{xtn|GB}}, {{xtn|TB}}, {{xtn|PB}}, {{xtn|EB}}, etc. over use of unambiguous IEC binary prefixes. {{crossref|For detailed discussion, see [[WT:Manual of Style (dates and numbers)/Archive/Complete rewrite of Units of Measurements (June 2008)]].}} }}
* when the majority of cited sources on the article topic use IEC prefixes;
* in a direct quote using the IEC prefixes;
* when explicitly discussing the IEC prefixes; or
* in articles in which both types of prefix are used with neither clearly primary, or in which converting all quantities to one or the other type would be misleading or lose necessary precision, or declaring the actual meaning of a unit on each use would be impractical.

==Currencies and monetary values<span id="Currencies"></span>==

{{shortcut|WP:$|WP:&pound;|WP:€|MOS:CURRENCY|MOS:MONEY}}
{{redirect|WP:CURRENCY|the WikiProject focusing on articles about currencies|Wikipedia:WikiProject Numismatics}}
{{redirect|WP:$|the policy on paid editing|Wikipedia:Paid-contribution disclosure}}

'''Choice of currency'''<!--Headings in this section formatted this way as permitted by MOS:PSEUDOHEAD: "If you want to reduce the size of the table of contents (TOC), use {{TOC limit}} ... In cases where {{TOC limit}} cannot be used because of lower-level headings elsewhere in the article, then using bold for the sub-sub-sub headings causes the least annoyance for screen reader users [though to do so is] a rarity."-->
* In '''country-specific articles''', such as [[Economy of Australia]], use the currency of the subject country.
* In '''non-country-specific articles''' such as [[Wealth]], use US dollars ({{xt|US$123}} on first use, generally {{xt|$123}} thereafter), euros ({{xt|&euro;123}}), or pounds sterling ({{xt|&pound;123}}).

'''Currency names'''
* Do not capitalize the names or denominations of currencies, currency subdivisions, coins and banknotes: not {{!xt|a Five-Dollar bill, four Quarters, and one Penny total six Dollars one Cent}} but {{xt|a five-dollar bill, four quarters, and one penny total six dollars one cent}}. ''Exception:'' where otherwise required, as at the start of a sentence or in such forms as {{xt|Australian dollar}}.
* To pluralize {{xtn|euro}} use the standard English plurals ({{xt|ten euros and fifty cents}}), not the [[Language and the euro#English|invariant plurals used for European Union legislation and banknotes]] ({{!xt|ten euro and fifty cent}}). For the adjectival form, use a hyphenated singular ({{xt|a two-euro pen and a ten-cent coin}}).
* Link the first occurrence of lesser-known currencies ({{xt|[[Mongolian tögrög]]s}}).<!--Should a symbol be introduced at this time?-->

'''Currency symbols'''<!--Symbols, signifiers, abbreviations? See [[ISO 4217]] and [[currency symbol]]s.-->
* In general, the first mention of a particular currency should use its full, unambiguous signifier (e.g. {{xt|A$52}}), with subsequent references using just the appropriate symbol (e.g. {{xt|$88}}), unless this would be unclear. {{em|Exceptions:}}
** In an article referring to multiple currencies represented by the same symbol (e.g. the dollars of the US, Canada, Australia, New Zealand, and other countries{{snd}}{{crossref|see {{section link|Currency symbols|dollar variants}}}}) use the full signifier (e.g. {{xt|US$}} or {{xt|A$}}, but not e.g. {{!xt|$US123}} or {{!xt|$123 (US)}}) each time, except (possibly) where a particular context makes this both unnecessary and undesirable.
** In articles entirely on EU-, UK- and/or US-related topics, all occurrences may be shortened ({{xt|&euro;26}}, {{xt|£22}} or {{xt|$34}}), unless this would be unclear.
* For the British [[pound sterling]] (GBP), use the {{xt|£}} symbol, with one horizontal bar, not the double-barred {{!xt|&#8356;}} (which is used for [[Italian lira]]). For non-British currencies that use pounds or a pound symbol (e.g. the [[Egyptian pound]], E£) use the symbol conventionally employed for that currency.
* If there is no common English abbreviation or symbol, follow the [[ISO 4217]] standard. {{crossref|See also [[List of circulating currencies]].}}
* Link the first occurrence of lesser-known currency symbols ({{xt|[[Mongolian tögrög|₮]]}})
{{see also|Wikipedia:Manual of Style/Abbreviations#Unicode abbreviation ligatures}}
{{Anchor|Formatting of monetary values}}'''Formatting'''

{{Anchor|Format}}<!--Old, imprecise heading, may be linked to.-->
* A period (full stop, <code>.</code>){{snd}}never a comma{{snd}}is used as the decimal point ({{xt|$6.57}}, not {{!xt|$6,57}}).
* For the grouping of digits (e.g. {{xt|&pound;1,234,567}}) see {{section link||Grouping of digits}}, above.
* Do not place a currency symbol {{em|after}} the accompanying numeric figures (e.g. {{!xt|123$}}, {{!xt|123&pound;}}, {{!xt|123&euro;}}) unless that is the normal convention for that symbol when writing in English: {{xt|smaller British coins include 1p, 2p, and 5p denominations}}.
* Currency abbreviations preceding a numeric value are {{em|unspaced}} if they consist of a nonalphabetic symbol alone ({{xt|&pound;123}} or {{xt|&euro;123}}), or end with a nonalphabetic symbol ({{xt|[[Brazilian real|R$]]123}}); but {{em|spaced}} (using {{t|nbsp}}) if completely alphabetic ({{xt|[[South African rand|R]]{{nbsp}}123}} or {{xt|[[Jordanian dinar|JD]]{{nbsp}}123}}).
* Ranges should be expressed giving the currency signifier just once: {{xt|$250{{ndash}}300}}, not {{!xt|$250{{ndash}}$300}}.
* {{xt|million}} and {{xt|billion}} should be spelled out on first use, and (optionally) abbreviated {{xt|M}} or {{xt|bn}} (both unspaced) thereafter: {{xt|She received &pound;70 million and her son &pound;10M}}; {{xt|the school's share was $250{{ndash}}300 million, and the charity's $400{{ndash}}450M}}.
* In general, a currency symbol should be accompanied by a numeric amount e.g. not {{!xt|He converted his US$ to A$}} but {{xt|He converted his US dollars to Australian dollars}} or {{xt|He exchanged the US$100 note for Australian dollars}}.
** Exceptions may occur in tables and infoboxes where space is limited e.g. {{xt|Currencies accepted: [[United States dollar|US$]], [[Swiss franc|SFr]], [[Pound sterling|GB&pound;]], [[Euro|&euro;]]}}. It may be appropriate to wikilink such uses, or add an explanatory note.

'''Conversions'''
* Conversions of {{em|less-familiar currencies}} may be provided in terms of more familiar currencies{{snd}}such as the US dollar, euro or pound sterling{{snd}}using an appropriate rate (which is often {{em|not}} the current exchange rate). Conversions should be in parentheses after the original currency, along with the convert-to year; e.g. {{xt|the grant in 2001 was 10,000,000 [[Swedish krona|Swedish kronor]] ($1.4M, &euro;970,000, or &pound;850,000 {{as of|2009|lc=on}})}}
* For {{em|obsolete currencies}}, provide an equivalent (formatted as a conversion) if possible, in the modern replacement currency (e.g. decimal pounds for historical pre-decimal pounds-and-shillings), or a US-dollar equivalent where there is no modern equivalent.
* In some cases, it may be appropriate to provide a conversion accounting for inflation or deflation over time. {{crossref|See {{tlx|Inflation}} and {{tlx|Inflation-fn}}.}}
* When converting among currencies or inflating/deflating, it is rarely appropriate to give the converted amount to more than three significant figures; typically, only two significant figures are justified: {{xt|the grant in 2001 was 10,000,000 [[Swedish krona|Swedish kronor]] ($1.4M, &euro;970,000, or &pound;850,000)}}, not {{!xt|($1,390,570, &euro;971,673 or &pound;848,646)}}

==Common mathematical symbols<span id="Minus sign"></span>==

{{shortcut|WP:COMMONMATH||MOS:MINUS}}
{{See also|Wikipedia:Manual of Style/Mathematics|Help:Displaying a formula}}
* The ''Insert'' menu below the editing window gives a more complete list of math symbols, and allows symbols to be inserted without the HTML encoding (e.g. <code>&amp;divide;</code>) shown here.
* Spaces are placed to left and right when a symbol is used {{nobr|[[binary operation|with two operands]]}} ({{xt|the sum 4 + 5}}), but no space is used when {{nobr|[[unary operation|there is one operand]]}} ({{xt|the value&nbsp;+5}}). ''Exception:'' spaces are usually omitted in inline fractions formed with <code>/</code>: {{xt|3/4}} not {{!xt|{{nobr|3 / 4}}}}.
* The {{tlx|mvar}} (for single-letter variables) and {{tlx|math}} (for more complicated expressions) templates are available to display mathematical formulas in a manner distinct from surrounding text.
* The {{tlx|nbsp}} and {{tlx|nowrap}} templates may be used to prevent awkward linebreaks.

{{clear right}}
{|class="wikitable" style="align: center; text-align: center;"
|+Common mathematical symbols
|-
! width=110|Symbol name
! width= 80|Example
! width=335|Markup
! Comments
|-
| rowspan=2| [[Plus sign|Plus /<br />positive]]
| {{math|''x'' + ''y''}}
| <syntaxhighlight lang="text" inline>{{math|''x'' + ''y''}}</syntaxhighlight>
| rowspan=2|
|-
| {{math|+''y''}}
| <syntaxhighlight lang="text" inline>{{math|+''y''}}</syntaxhighlight>
|-
| rowspan=2|[[Minus sign|Minus /<br />negative]]
| {{math|''x'' &minus; ''y''}}
| <syntaxhighlight lang="text" inline>{{math|''x'' &minus; ''y''}}</syntaxhighlight>
| rowspan=2|Do not use hyphens ({{!xt|<syntaxhighlight lang="text" inline>-</syntaxhighlight>}}) or dashes ({{!xt|{{tlx|ndash}}}} {{nobr|or {{!xt|{{tlx|mdash}}}}).}}
|-
| {{math|&minus;''y''}}
| <syntaxhighlight lang="text" inline>{{math|&minus;''y''}}</syntaxhighlight>
|-
| rowspan=2| [[Plus-minus sign|Plus-minus /<br />minus-plus]]
| 41.5 &plusmn; 0.3
| <syntaxhighlight lang="text" inline>41.5 &plusmn; 0.3</syntaxhighlight>
| rowspan=3|
|-
| {{math|1={{nobr|1= &minus;(&plusmn;''a'') = &#8723;''a''}}}}
| {{nobr|1=<syntaxhighlight lang="text" inline>{{math|1=&minus;(&plusmn;''a'') = &#8723;''a''}}</syntaxhighlight> }}
|-
| Multiplication,<br />dot
| {{math|''x'' &sdot; ''y''}}
| <syntaxhighlight lang="text" inline>{{math|''x'' &sdot; ''y''}}</syntaxhighlight> 
|-
| [[Multiplication sign|Multiplication]],<br />cross
| {{math|''x'' &times; ''y''}}
| <syntaxhighlight lang="text" inline>{{math|''x'' &times; ''y''}}</syntaxhighlight> 
| Do not use the letter {{!xt|x}} to indicate multiplication. However, an {{em|unspaced}} {{xt|x}} may be used as a substitute for "by" in common terms such as [[4x4|{{xt|4x4}}]].
|-
| [[Division sign|Division]], obelus
| {{math|''x'' &divide; ''y''}}
| <syntaxhighlight lang="text" inline>{{math|''x'' &divide; ''y''}}</syntaxhighlight>
|
|-
| [[Equal sign|Equal / equals]]
| {{math|1=''x'' = ''y''}}
| <syntaxhighlight lang="text" inline>{{math|1=''x'' = ''y''}}</syntaxhighlight> or<br /><syntaxhighlight lang="text" inline>{{math|''x'' {{=}} ''y''}}</syntaxhighlight>
| Note the use of <syntaxhighlight lang="text" inline>1=</syntaxhighlight> or <syntaxhighlight lang="text" inline>{{=}}</syntaxhighlight> to make the template parameters work correctly
|-
| [[Not equal sign|Not equal]]
| {{math|''x'' &ne; ''y''}}
| <syntaxhighlight lang="text" inline>{{math|''x'' &ne; ''y''}}</syntaxhighlight>
| rowspan=6|
|-
| [[Approximate sign|Approx. equal]]
| {{math|''&pi;'' &asymp; 3.14}}
| <syntaxhighlight lang="text" inline>{{math|''&pi;'' &asymp; 3.14}}</syntaxhighlight>
|-
| [[Less than sign|Less than]]
| {{math|''x'' &lt; ''y''}}
| <syntaxhighlight lang="text" inline>{{math|''x'' &lt; ''y''}}</syntaxhighlight>
|-
| [[Less than or equal to|Less or equal]]
| {{math|''x'' &le; ''y''}}
| <syntaxhighlight lang="text" inline>{{math|''x'' &le; ''y''}}</syntaxhighlight>
|-
| [[Greater than sign|Greater than]]
| {{math|''x'' &gt; ''y''}}
| <syntaxhighlight lang="text" inline>{{math|''x'' &gt; ''y''}}</syntaxhighlight>
|-
| [[Greater than or equal to|Greater or equal]]
| {{math|''x'' &ge; ''y''}}
| <syntaxhighlight lang="text" inline>{{math|''x'' &ge; ''y''}}</syntaxhighlight>
|}

==Geographical coordinates==

<div style="float:right; width:100px;">{{Shortcut|MOS:COORDS|WP:COORDINATES}}</div>

:{{crossref|For draft guidance on, and examples of, coordinates for linear features, see [[Wikipedia:WikiProject Geographical coordinates/Linear]].}}

:'''Quick guide''':

{{coord how-to}}
[[Geographical coordinates]] on Earth should be entered using a template to standardise the format and to provide a link to maps of the coordinates. As long as the templates are adhered to, a robot performs the functions automatically.

First, [[Wikipedia:Obtaining geographic coordinates|obtain the coordinates]]. Avoid [[Wikipedia:WikiProject Geographical coordinates#Precision|excessive precision]].

The {{tlx|Coord}} template offers users a choice of display format through [[Help:User style|user styles]], emits a [[Geo microformat]], and is recognised (in the {{em|title}} position) by the "nearby" feature of Wikipedia's mobile apps and by external service providers such as Google Maps and Google Earth, and Yahoo. Infoboxes automatically emit {{tlx|Coord}}.

The following formats are available.
* For degrees only (including decimal values): {{tlc|coord|2={{var|dd}}|3={{var|N/S}}|4={{var|dd}}|5={{var|E/W}}}}
* For degrees/minutes: {{tlc|coord|2={{var|dd}}|3={{var|mm}}|4={{var|N/S}}|5={{var|dd}}|6={{var|mm}}|7={{var|E/W}}}}
* For degrees/minutes/seconds: {{tlc|coord|2={{var|dd}}|3={{var|mm}}|4={{var|ss}}|5={{var|N/S}}|6={{var|dd}}|7={{var|mm}}|8={{var|ss}}|9={{var|E/W}}}}

where:
* {{var|dd}}, {{var|mm}}, {{var|ss}} are the degrees, minutes and seconds, respectively;
* {{var|N/S}} is either <kbd>N</kbd> for northern or <kbd>S</kbd> for southern [[latitude]]s;
* {{var|E/W}} is either <kbd>E</kbd> for eastern or <kbd>W</kbd> for western [[longitude]]s;
* negative values may be used in lieu of <kbd>S</kbd> and <kbd>W</kbd> to denote Southern and Western [[Hemisphere of the Earth|Hemispheres]]

For example:

For the city of [[Oslo]], located at 59° 54&prime; 50&Prime; N, 10° 45&prime; 8&Prime; E:
: <code><nowiki>{{coord|59|54|50|N|10|45|08|E}}</nowiki></code>{{snd}}which becomes {{coord|59|54|50|N|10|45|08|E}}

For a country, like [[Botswana]], with no source on an exact geographic center, less precision is appropriate due to uncertainty:
: <code><nowiki>{{coord|22|S|24|E}}</nowiki></code>{{snd}}which becomes {{coord|22|S|24|E}}

Higher levels of precision are obtained by using seconds:
: <code><nowiki>{{coord|33|56|24|N|118|24|00|W}}</nowiki></code>{{snd}}which becomes {{coord|33|56|24|N|118|24|00|W}}

Coordinates can be entered as decimal values:
: <code><nowiki>{{coord|33.94|S|118.40|W}}</nowiki></code>{{snd}}which becomes {{coord|33.94|S|118.40|W}}

Increasing or decreasing the number of decimal places controls the precision. Trailing zeros may be added as needed to give both values the same appearance.

[[Heathrow Airport]], [[Amsterdam]], [[Jan Mayen]] and [[Mount Baker]] are examples of articles that contain geographical coordinates.

Generally, the larger the object being mapped, the {{em|less precise}} the coordinates should be. For example, if just giving the location of a city, precision greater than degrees (°), minutes (&prime;), seconds (&Prime;) is not needed, which sufficient to locate, for example, the central administrative building. Specific buildings or other objects of similar size would justify precisions down to 10{{nbsp}}meters or even one meter in some cases (1″ ~15{{nbsp}}m to 30{{nbsp}}m, 0.0001° ~5.6{{nbsp}}m to 10{{nbsp}}m).

The final field, following the E/W, is available for attributes such as <code>type:</code>, <code>region:</code>, or <code>scale:</code> {{crossref|(the codes are documented at {{section link|Template:Coord/doc#Coordinate parameters}})}}.

When adding coordinates, please remove the {{tlx|coord missing}} tag from the article, if present (often at the bottom).

{{Crossref|For more information, see [[Wikipedia:WikiProject Geographical coordinates|the geographical coordinates WikiProject]].}}

Templates other than {{tlx|coord}} should use the following variable names for coordinates: {{var|lat_d}}, {{var|lat_m}}, {{var|lat_s}}, {{var|lat_NS}}, {{var|long_d}}, {{var|long_m}}, {{var|long_s}}, {{var|long_EW}}.

==See also==

* [[Wikipedia:Naming conventions (numbers and dates)]]
* [[Wikipedia:Date formattings]]
* [[m:Help:Date formatting feature]] at Meta
* {{section link|m:Help:Calculation|Displaying numbers and numeric expressions}} at Meta

==Notes==

{{Notelist|35em}}

==References==

{{Reflist|35em}}

{{Manual of Style}}
{{Math templates}}

[[Category:Wikipedia Manual of Style (formatting)]]
[[Category:Wikipedia naming conventions|Dates and numbers]]