Manual of Style/Dates and numbers

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. For numbers, dates, and similar items in Wikipedia article titles, see the "Naming conventions (numbers and dates)" guideline.

Where this manual gives options, maintain consistency within an article unless there is a good reason to do otherwise. The 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. 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.

General notes

Quotations, titles, etc.

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 racketed interpolation article text, or footnotes.

Non-breaking spaces

Guidance on the use of non-breaking spaces ("hard spaces") is given in some sections below, but not all situations in which hard spaces ( or  ) or may be appropriate are described.

Chronological items

Statements likely to become outdated

Except on pages that are inherently time-sensitive and updated regularly (e.g. the "Current events" portal), terms such as , , , , , , , , and should usually be avoided in favor of phrases such as , , and . Wording can usually be modified to remove the "now" perspective: not but ; not but or .See also this July 2022 RfC. For current and future events, use phrases such as or to signal the time-dependence of the information; use the template (or ) in conjunction.

Relative-time expressions are acceptable for very long periods, such as geological epochs:

Dates, months, and years

* These requirements do not apply to dates in quotations or titles; .
* Special rules apply to citations; .
* See also Wikipedia:Overview of date formatting guidelines.

Formats

* 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 .
* For issues related to dates in sortable tables, and , or consider using
* Phrases such as (or , but not ), , , and are proper names, to which rules for dates do not apply ().

=Consistency

=

* Dates in article body text should all use the same format: , not .
* 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 "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 citation style being used (but all-numeric date formats other than must still be avoided).
: For example, publication dates within a single article might be in one, but only one, of these formats (among others):
::
::
:If an article uses a template such as , Citation Style 1 and 2 templates automatically render dates (, , , etc) in the style specified by the "Use" template, regardless of the format they are entered in. See Template:Use mdy dates#Auto-formatting citation template dates.
* 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
**
: For example, access/archive dates within a single article might be in one, but only one, of these formats (among others):
::
::
::
: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

=

For any given article, the choice of date format and the choice of national variety of English (see ) 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) ; for most other English-speaking countries it is .
* Articles related to Canada may use either format with (as always) consistency within each article.
* 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

=

* 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

* The default calendar eras are Anno Domini ( and ) and Common Era ( and ). Either convention may be appropriate for use in Wikipedia articles depending on the article context. Apply with regard to changes from one era to the other.
** Use either the BCAD or the BCECE notation consistently within the same article. Exception: do not change 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 ) 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 (, not ). It is advisable to use a non-breaking space.
** AD appears before or after a year (, ); the other abbreviations appear only after (, , ).
** In general, omit CE or AD, unless to avoid ambiguity or awkwardness
*** Typically, write not nor
*** But (not simply ) may avoid confusion unless the era is clear from context.
*** One- and two-digit years may look more natural with an era marker ( or , not nor
*** Ranges beginning in BC/BCE should specify the ending era: write or or , but not .
* Uncalibrated (BCE) radiocarbon dates: 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 – , or at least indicate the date type – . 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 January1, 1950.) Write or or but not forms such as and . If one of the abbreviated forms is used, link to ''Before Present'' on first use:
* 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: , or .
** 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: (The expressions and refer to the same year.)

Julian and Gregorian calendars

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 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 Continent of Europe from 1582, the British Empire from 14September 1752, and Russia from 14February 1918 .
* Dates before 15October 1582 (when the Gregorian calendar was first adopted in some places) are normally given in the Julian calendar.
* Dates after 4October1582 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 1January even if a different start-of-year date was observed in the place being discussed.
* Dates for Roman history before 45BC 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 footnote). The guidance above is in line with the usage of reliable sources such as ''American National Biography'', '' Oxford Dictionary of National Biography'', and '' Encyclopædia Britannica''.

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 . If a date appears without being specified as Old Style or New Style, tagging that date with will add the page to :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

* A simple yearyear range is written using an en dash (–, – or ), not an em dash, hyphen, or slash; this dash is (that is, with no space on either side); and the end year is usually given in full:
** ; (not ); (not )
**
** Although non-abbreviated years are generally , two-digit ending years (, but never or ) be used in any of the following cases: (1) two consecutive years; (2) 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. 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 (, not ) or for years from the first millennium (, not ).
** The () 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 en dash as well:
** dayday: ; ; .
** monthmonth: ; ; (but uses a en dash; )
* In certain cases where at least one item on either side of the en dash contains a space, then a en dash () is used. For example:
** between specific dates in different months: ;
** between dates in different years:
***
***
***
** between months in different years: ;
***
** Where era designations, c. or other modifiers are present :
*** if the modifier applies to only one of the two endpoints of the range, use a en dash: , ,
*** if the modifier applies to the range as a whole, the modifier: , , , }, }.

* MOS:DATED says "terms such as ... 'present' should usually be avoided". For ranges, if "to present" or "present" is used, the current year (or, in cases where necessary, date) of "present" at the time of writing should be included. Thus —if writing in —is preferable to . If the "from" date has an internal space, a spaced en dash is used. Other constructions may be more appropriate in prose . An alternative form is .

:In tables and infoboxes where space is limited, ''pres.'' may be used (). Do not use incomplete-looking constructions such as } and
:*Consider adding the , or templates to such constructions, depending on how important it is for editors to keep "present" up to date.

*

For a person still living: , not or .

Do not use * to indicate ''born''; use b. only where space is limited e.g. tables and infoboxes; use either born or b. consistently in any given table column.

*

Where birthdate is unknown: or

Do not use † to indicate ''died''; use d. only where space is limited, with consistency within any given table column.

*

An overnight period may be expressed using a slash between two contiguous dates: or .

Or use an en dash: (unspaced) ; (spaced) .

* Use an en dash, or a word such as ''from'' or ''between'', but not both: (not ); (not )
* The template can keep ages current in infoboxes and so on:
** returns:
** -year-old returns:
** years old returns:
* Date mathematics templates are available for other age calculations.

Uncertain, incomplete, or approximate dates

* To indicate "around", "approximately", or "about", the use of the template is preferred over , , , , , , , or :
**
**
* Where both endpoints of a range are approximate, c. should appear before each date (the two-argument form of does this):
** (not )
** (not )
* Where birth/death limits have been inferred from known dates of activity:
**
**
**
* When birth and death dates are unknown, but the person is known to have been active ("flourishing") during certain years, , fl., or may be used:
**
**
: 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 or AH year conversion, or a known age at death):
**
* Other forms of uncertainty should be expressed in words, either in article text or in a footnote: . Do not use a question mark (), because it fails to communicate the nature of the uncertainty.
* Where or a similar form appears ''which applies only to one of the two endpoints of the range'', use a spaced en dash ().
** ''Examples'': , }, , }.
** ''Markup'': , , , .
* Where a modifier ''applies to the range as a whole'', such as and , use a spaced or unspaced en dash as appropriate to the range if this modifier is disregarded.
** ''Examples'': , , , , .
* Some modifiers, such as , , , and , sometimes apply to only one endpoint, and sometimes to the whole range. Whether the en dash should be spaced or unspaced should still be determined by the above guidelines, but consider rephrasing if the result is ambiguous or possibly confusing.
** and mean two different things, which may not be obvious to the reader.
** } can have two different meanings, and which one is meant may not be clear.
** clearly has applying only to one endpoint, but the range is ambiguous. Consider using , , or , depending on what is meant.
** Technically, is currently unambiguous (because there is no Taishō 57), but it is better to use both era designations in this case: .
* Ideally a non-breaking space should follow very short modifiers such as , , , , and

Times of day

Context determines whether the 12- or 24-hour clock is used. In all cases, colons separate hours, minutes, and (where present) seconds, e.g. or . Use figures ( or ) rather than words ().
* 12-hour clock times end with lower-case or , or or , preceded by a non-breaking space, e.g. or (markup: 2:30p.m. or 2:30pm), not or . Hours should not have a leading zero (e.g. , not ). Usually, use and rather than and ; 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 ( not ). Hours under 10 should have a leading zero (). The time refers to midnight at the start of a date, to noon, and to midnight at the end of a date, but should not be used for the first hour of the next day (e.g. use for ten minutes after midnight, not ).

Time zones

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 December7, 1941 (Hawaii time/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:

Alternatively, include just the UTC offset:

Rarely, the time zone in which an event took place has since changed; for example, China until 1949 was divided into 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; 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.

Days of the week

* Where space is limited (e.g. tables), days of the week may be abbreviated as , , , , , , (without dots, i.e. not , , etc.).

Seasons of the year

* Generally, seasons are uncapitalized () except when personified: .
* Avoid the use of seasons to refer to a particular time of year () as such uses are ambiguous: the seasons are six months apart in the northern and southern hemispheres; winter in the northern hemisphere spans two calendar years, as does summer in the southern hemisphere; and areas near the equator have only wet and dry seasons. Unambiguous alternatives include ; ; ; .
** Referring to a season by name is appropriate when it is part of a formal or conventional name or designation (; ; ; ; ; ).

Decades

* To refer to a decade as a chronological period (not with reference to a social era or cultural phenomenon), always use four digits as in . Do not use , , or (unless a possessive is actually meant).
** Prefixes should be hyphenated (; ).
** Adjectives should not be hyphenated ().
* 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, but only in well-established phrases seen in reliable sources: ; ; but . Do not write: ; ; or .
** Another alternative (where seen in reliable sources) is to spell the decade out, capitalized: .

Centuries and millennia

The sequence of numbered years in dates runs ; there is no " year zero".
* Treat the 1st century AD as years , the 17th century as , and the second millennium as ; similarly, the 1st century BC/BCE was BC/BCE, the 17th century BC/BCE was BC/BCE, and the second millennium BC/BCE.
* Centuries and millennia are identified using either Arabic numerals () or words (), with in-article consistency ( MOS:ORDINAL notwithstanding). When used adjectivally they contain a hyphen ( or ). Do not use superscripts ().
* Do not capitalize (; )
* Do not use Roman numerals ().
* refers to the period (), while strictly refers either to () or ()
** When using forms such as , ensure there is no ambiguity as to whether the century or just its first decade is meant.
*

Long periods of time

* When the term is frequent, combine (years) or (years ago) with (thousand): , ; (million): , ; and (short-scale billion): , .
* In academic contexts, SI annus-based units are often used: (kiloannus), (megaannus), and (gigaannus).
* Show the meaning parenthetically, and consider linking to the appropriate section of the Year article on first occurrence and where the use is a standalone topic of interest. In source quotations, use square brackets:

Numbers

Numbers as figures or words

Generally, in article text:
* Integers from zero to nine are spelled out in words.
* Integers greater than nine may be expressed either in numerals or in words ( or , or , or ). When written as words, integers from 21 to 99 that are not multiples of 10 are hyphenated (including when part of a larger number): and but and are not.
* Other numbers are given in numerals (, ) or in forms such as (or ''billion'', ''trillion'', etc.but rarely ''thousand'' or ''hundred''). Markup:
** ''Billion'' and ''trillion'' are understood to represent their short-scale values of 10⁹(1,000,000,000) and 10¹²(1,000,000,000,000), respectively. Keep this in mind when translating articles from non-English or older sources.
** (unspaced, capitalized) or (unspaced), respectively, may be used for "million" or "billion" after a number, when the word has been spelled out at the first occurrence ().
** SI prefixes and symbols, such as (), () and (), 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:
** Sometimes, the 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 Indian numbering system is conventionally used for certain things (especially monetary amounts) in South Asian English. This is discouraged in Wikipedia articles by .
*** When it is done anyway, for contextually important reasons, link the first spelled-out instance of each quantity (e.g. crore, 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 and 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 . When converting a currency amount, use the exchange rate that applied at the time being written about; the template can be used for this purpose.
*** Group digits in Western thousands-based style (e.g., ; not ); .
*** The variety of English does not uniquely determine the method of numbering in an article. Other considerationssuch as conventions used in mathematics, science, and engineeringmay also apply. The choice and order of formats and conversions is a matter of editorial discretion and consensus at the article.

Notes and exceptions:
* Avoid beginning a sentence with a figure:
** Use: Or:
** Not:
** Use:
** Not: (Nor: comparable numbers should be both written in words or both in figures.)
* In tables and infoboxes, quantities are expressed in figures (); but numbers within a table's explanatory text and comments follow the general rule.
* Numbers in mathematical formulae are never spelled out (} not ), and "numbers as numbers" are rarely spelled out in other mathematical contexts ( not ; but and ).
* Sport scores and vote tallies should be given as figures, even if in the zero-to-nine range (; and ).
* Comparable values nearby one another should be all spelled out or all in figures, even if one of the numbers would normally be written differently: or , but not .
**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): ; ; ; .
* Adjacent quantities not comparable should ideally be in or , not or .
** Avoid awkward juxtapositions: , not .
* Sometimes figures and words carry different meanings; for example, implies there is a single exception (without specifying which), while means that locker number1 was the only locker not searched.
* Proper names, technical terms, and the like are never altered: , , , , , , , , , , ,
* Figures as figures: Use a figure when the figure itself (its glyph, shape, etc.) is meant: ; .
* Only figures are used with unit ( not ); but figures or words may be used with unit ( or ), subject to the provisions above.

Ordinals

* For guidance on choosing between e.g. and , see ''generally'', for single-digit ordinals write , not .
* In "suffix" forms, use two-letter suffixes: and so on ( not ). Do not superscript ().
* Do not use ordinals for dates (see MOS:BADDATE).
* In English text, do not use a dot () or the ordinal indicator (). The masculine or feminine ordinal indicator is acceptable in names, quotations, etc. from languages that conventionally use it. An Italian example: not or . Use HTML markup for languages that don't have a special character but conventionally use a superscript, like in French.
* Regnal numbers are normally written with ASCII Roman numerals (without suffix, e.g. not or ).

Number ranges

Like , number ranges and page ranges should state the full value of both the beginning and end of the range, separated by an en dash: or . Except in quotations, avoid abbreviated forms such as and , 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 :
*
*

Singular versus plural

* Nouns following simple fractions are singular (; ; ).
* Nouns following mixed numbers are plural (; ).
* 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 (; ; ; but ; ; ).
* The same rules apply to numbers given in words (; ; ; ).

Fractions and ratios

* Spelled-out fractions are hyphenated: .
* Where numerator and denominator can each be expressed in one word, a fraction is usually spelled out (e.g. ; ); use figures if a fraction appears with a symbol (e.g. markup:  mi, not or ). A common exception is a series of values: .
* Mixed numbers are usually given in figures, unspaced (not or but markup: ). In any case the integer and fractional parts should be consistent (not ).
* Metric (SI) measurements generally use decimals, not fractions (, not ).
* Non-metric (imperial and US customary) measurements may use fractions or decimals (;); 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 rather than ). The use of is discouraged in favor of one of these styles:
** $\textstyle\frac$markup: < math>\textstyle\frac
** markup:
** markup: 1/2
* Do not use precomposed fraction characters such as (deprecated markup: ½ or ½).
** Except: If ¼, ½, and ¾These three characters are in ISO/IEC 8859-1 and work in screen readers. are the only fractions needed, they may be used in an article body, or category name, maintaining typographical consistency within an article where possible. (Examples: Ranma ½, chess notation, :4 ft 6½ in gauge railways‎.)
* Ordinal suffixes such as should not be used with fractions expressed in figures (not ; , but ; ; ).
* Dimensionless ratios (i.e. those without accompanying units) are given by placing a colon between integers, or placing ''to'' between numbers-as-words: or , not or
** Use a colon (spaced) when one or more decimal points is present
** Do not use the colon form where units are involved ()instead see ''ratios'' section of table at § Unit names and symbols, below.

Decimals

* Use a period/full point (.) as the decimal separator, a comma: , not .
* Numbers between −1 and +1 require a leading zero (, not ); exceptions are sporting performance averages () and commonly used terms such as .
* Indicate repeating digits with an overbar e.g. gives . (Consider explaining this notation on first use.) Do not write e.g. because it resembles notation for uncertainty.

Grouping of digits

* In general, digits should be grouped and separated either by commas or by narrow gaps ( 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. ; ; ; ).
*** Numbers with exactly four digits left of the decimal point may optionally be grouped (either or ), 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: produces this formatting.
** Grouping with narrow gaps
*** Digits are grouped both sides of the decimal point (e.g. ; ; ).
*** Digits are generally grouped into threes. Right of the decimal point, practice is to have a final group of four in preference to leaving an "orphaned" digit at the end (, but would also be acceptable). In mathematics-oriented articles long strings may be grouped into fives (e.g. ).
*** This style is especially recommended for articles related to science, technology, engineering or mathematics, though in these contexts there may be cases in which grouping confuses rather than clarifies. (For example, for fractions written in horizontal format, adding spaces to a fraction like 123456/127 would cause it to be misread as 123 or 1.)
*** Markup: Templates or may be used to produce this formatting. Note that use of space character as a separator in numbers, including non-breaking space, is problematic for screen readers. Screen readers read out each of digits as separate numbers (e.g. 30000 is read as "thirty zero zero zero"). The output of and is compatible with screen readers.
* 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.
* Four-digit page numbers and four-digit calendar years should never be grouped (not , but or ).

Percentages

* In the body of non-scientific/non-technical articles, (American English) or (British English) are commonly used: ; ; . Ranges are written or , not .
* In the body of scientific/technical articles, and in of any article, the symbol % (unspaced) is more common: , not or . Ranges: , not or .
* When expressing the difference between two percentages, do not confuse a percentage change with a change in percentage points.

Scientific and engineering notation

* Scientific notation always has a single nonzero digit to the left of the point: not , but .
* Engineering notation is similar, but with the exponent adjusted to a multiple of three: .
* Avoid mixing scientific and engineering notations ().
* In a table column (or other presentation) in which all values can be expressed with a single power of 10, consider giving e.g. once in the column header, and omitting it in the individual entries. (Markup: )
* In both notations, the number of digits indicates the precision. For example, means rounded to the nearest thousand; to the nearest hundred; to the nearest ten; and to the nearest unit.

Markup: and may be used to format exponential notation.

Uncertainty and rounding

* Where explicit uncertainty information (such as a margin of error) is available and appropriate for inclusion, it may be written in various ways:
**
** (not used with scientific notation)
**
** (equivalent to )
**
** Markup: , , and may be used to format uncertainties.
* Where explicit (or is unimportant for the article's purposes), round to an appropriate number of significant digits; 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.
**
**
** (not )
** (not an official figure unlikely to be accurate at full precision)
** (unusual case in which the full-precision official figure is truly informative)
** (likely that accurate and precise figures were determined)
** (unlikely that any precise number can be accurate, even if an official figure is issued)
** (in reporting conflicting information, give detail sufficient to make the contrast intelligible)
** (not ).
* The number of decimal places should be consistent within a list or context (, not ), unless different precisions are actually intended.
* It may sometimes be appropriate to note the of uncertainty information, especially where such information is normally provided and necessary for full interpretation of the figures supplied.
**
* The 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.
** (heights are conventionally reported only to the nearest inch, even though greater precision may be available in principle)
** ("about" because here the precise value is unknown, with substantial uncertainty)
* The reader may be assumed to interpret large round numbers () as approximations. Writing a quantity in words (), especially if the indefinite article (''a''/''an'') is used instead of the word ''one'' (), can further emphasize its approximate nature.
*

Non–base 10 notations

* In computer-related articles, use the prefix 0x for hexadecimal and 0b for binary, unless there is a strong reason to use some other notation. Explain these prefixes in the article's introduction or on first use.
* In all other articles, use base: , . Markup: ,
* For bases above 10, use symbols conventional for that base (as seen in reliable sources) e.g. for base 16 use .
* For octal, use . Avoid using a prefix unless it is needed for computer code samples, in which case explain the prefix on first use.

Mathematical formulae

There are multiple ways to display mathematical formulae, covered in detail at . One uses special MediaWiki markup using LaTeX syntax, which is capable of complex formulae; the other relies on conventionalized HTML formatting of simple formulae.

The markup is displayed as a 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.

Do not put markup in headings.

Units of 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. . For details on when and how to provide a conversion, see the section . The choice of primary units depends on the circumstances, and should respect the principle of " strong national ties", where applicable:
* In non-scientific articles with strong ties to the United States, the primary units are US customary (pounds, 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, except that:
** UK engineering-related articles, including those on bridges and tunnels, generally use the system of units in which the subject project was drawn up (but road distances are given in imperial units, with a metric conversionsee next bullet);
** the primary units for distance/length, speed and fuel consumption are 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/inches and stones/pounds;
** imperial pints are used for quantities of draught beer/cider and bottled milk;
* In all other articles, the primary units chosen will be SI units, 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, hands for heights of horses, etc.).

* 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: .
** Or use ''about'' to emphasize which is the statutory, exact value: .
* Nominal quantities (e.g. 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 .
* Where the article's primary units differ from the units given in the source, the template's , order=flip flag can be used; this causes the unit to be shown as secondary in the article, and the unit to be shown as primary: →

Unit conversions

Where English-speaking countries use different units for the same quantity, provide a conversion in parentheses: ; . 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 US customary system, or vice versaand in particular, where those systems give a single term different definitionsa double conversion may be appropriate: (markup: ); (markup: ).
* 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 ().
** In some topic areas (for example maritime subjects where nautical miles are the primary units, or American football where 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 unitpossibly giving the conversion factor to other, familiar units in a parenthetical note or a footnoteand 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.
* Converted quantity values should use a similar to that of the source quantity value, so , not . Small numbers, especially if approximate, may need to be converted to a range where rounding would cause a significant distortion, so , not . 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).
* (and other 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.
* may be added to articles needing general attention regarding choice of units and unit conversions.

Unit names and symbols

:
:* 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. ).
** Exception: Certain units are generally represented by their symbols (e.g. rather than ) even on first use, though their unit names may be used for emphasis or clarity ().
** Exception: Consider using ''inches'' (but not ''in.'') in place of ''in'' where the latter might be misread as a prepositionbut not where the value is followed by a parenthesized conversion e.g. , or is part of such a conversion ().
* 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 namesymbol pair on first use, linking the unit name ().
* Ranges use unspaced en dash () if only one unit symbol is used at the end (e.g. ), and spaced en dash () if two symbols are used (e.g. ); 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: ; ; ; ).
* Lengthwidth, lengthwidthheight and similar dimensions may be separated by the multiplication sign (× or ×) or the word by.
** The 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:
*** , not , , nor
***
***
** With , the unit need be given only once if it is the same for all dimensions: or
** The unspaced letter may be used in common terms such as .

Specific units

* The following table lists only units that need special attention.
* The ''SI Brochure'' should be consulted for guidance on use of other SI and non-SI units.

Quantities of bytes and bits

In quantities of bits and bytes, the prefixes (symbol or ), (), (), (), etc., are ambiguous in general usage. The meaning may be based on a decimal system (like the standard SI prefixes), meaning 10³, 10⁶, 10⁹, 10¹², etc., or it may be based on a binary system, meaning 2¹⁰, 2²⁰, 2³⁰, 2⁴⁰, etc. The binary meanings are more commonly used in relation to solid-state memory (such as RAM), while the decimal meanings are more common for data transmission rates, disk storage and in theoretical calculations in modern academic textbooks.

Follow these recommendations when using these prefixes in Wikipedia articles:
* Following the SI standard, a lower-case should be used for "kilo-" whenever it means 1000 in computing contexts, whereas a capital 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 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 ( 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 rates, 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:
**
**
**
* Avoid combinations with inconsistent form such as . Footnotes, such as those seen in /en.wikipedia.org/w/index.php?title=Power_Macintosh_5500&oldid=218088888 may be used for disambiguation.
* Unless explicitly stated otherwise, one byte is eight bits .

The IEC prefixes (symbol ), (), (), etc., are generally not to be used except:
* 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

Choice of currency
* 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 ( on first use, generally thereafter), euros (), or pounds sterling ().

Currency names
* Do not capitalize the names or denominations of currencies, currency subdivisions, coins and banknotes: not but . ''Exception:'' where otherwise required, as at the start of a sentence or in such forms as .
* To pluralize use the standard English plurals (), not the invariant plurals used for European Union legislation and banknotes (). For the adjectival form, use a hyphenated singular ().
* Link the first occurrence of lesser-known currencies (e.g. ).

Currency symbols
* In general, the first mention of a particular currency should use its full, unambiguous signifier (e.g. ), with subsequent references using just the appropriate symbol (e.g. ), unless this would be unclear.
** 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) use the full signifier (e.g. or , but not e.g. or ) 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 (, or ), unless this would be unclear.
* For the British pound sterling (GBP), use the symbol with one horizontal bar (), not the double-barred symbol (). (Whether a pound sign uses one or two bars is purely a type-design choice.) For non-British currencies that use "pounds", use the symbol or abbreviation conventionally employed for that currency, if any.
* If there is no common English abbreviation or symbol, follow the ISO 4217 standard.
* Link the first occurrence of lesser-known currency symbols (e.g. )

Formatting

* A period (full stop, .)never a commais used as the decimal point (, not ).
* For the grouping of digits (e.g. ) see , above.
* Do not place a currency symbol the accompanying numeric figures (e.g. , , ) unless that is the normal convention for that symbol when writing in English: .
* Currency abbreviations preceding a numeric value are if they consist of a nonalphabetic symbol alone ( or ), or end with a nonalphabetic symbol (); but (using ) if completely alphabetic ( or ).
* Ranges should be expressed giving the currency signifier just once: , not .
* and should be spelled out on first use, and (optionally) abbreviated or (both unspaced) thereafter: ;
* In general, a currency symbol should be accompanied by a numeric amount e.g. not but or .
** Exceptions may occur in tables and infoboxes where space is limited e.g. . It may be appropriate to wikilink such uses, or add an explanatory note.

Conversions
* Conversions of may be provided in terms of more familiar currenciessuch as the US dollar, euro or pound sterlingusing an appropriate rate (which is often the current exchange rate). Conversions should be in parentheses after the original currency, along with the convert-to year; e.g.
* For , 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.
* 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: , not

Common mathematical symbols

* 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. ÷) shown here.
* Spaces are placed to left and right when a symbol is used (), but no space is used when (). ''Exception:'' spaces are usually omitted in inline fractions formed with /: not .
* The (for single-letter variables) and (for more complicated expressions) templates are available to display mathematical formulas in a manner distinct from surrounding text.
* The and templates may be used to prevent awkward linebreaks.

Geographical coordinates

:

:Quick guide:

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, obtain the coordinates. Avoid excessive precision.

The template offers users a choice of display format through user styles, emits a Geo microformat, and is recognised (in the 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 .

The following formats are available.
* For degrees only (including decimal values):
* For degrees/minutes:
* For degrees/minutes/seconds:

where:
* , , are the degrees, minutes and seconds, respectively;
* is either N for northern or S for southern latitudes;
* is either E for eastern or W for western longitudes;
* negative values may be used in lieu of S and W to denote Southern and Western Hemispheres

For example:

For the city of Oslo, located at 59° 54′ 50″ N, 10° 45′ 8″ E:
: which becomes

For a country, like Botswana, with no source on an exact geographic center, less precision is appropriate due to uncertainty:
: which becomes

Higher levels of precision are obtained by using seconds:
: which becomes

Coordinates can be entered as decimal values:
: which becomes

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 the coordinates should be. For example, if just giving the location of a city, precision greater than degrees (°), minutes (′), seconds (″) is not needed, which suffice to locate, for example, the central administrative building. Specific buildings or other objects of similar size would justify precisions down to 10meters or even one meter in some cases (1″ ~15m to 30m, 0.0001° ~5.6m to 10m).

The final field, following the E/W, is available for attributes such as type:, region:, or scale: .

When adding coordinates, please remove the tag from the article, if present (often at the bottom).

Templates other than should use the following variable names for coordinates: , , , , , , , .

See also

* Wikipedia:Date formattings
* m:Help:Date formatting feature at Meta
* at Meta

Notes

References

{{Math templates

Wikipedia Manual of Style (formatting)
Dates and numbers