Wikipedia:Manual of Style/Dates and numbers

This part of the Manual of Style helps editors to achieve consistency in the use and formatting of numbers, dates, times, measurements, currencies, and coordinates in Wikipedia articles. Consistency in style and formatting promotes clarity and cohesion; this is especially important within an article. The goal is to make the whole encyclopedia easier and more intuitive to use. Try to write so the text cannot be misunderstood, and take account of what is likely to be familiar to readers. The less that readers have to look up definitions, the easier the text will be to understand.

Where this manual provides options, consistency should be maintained 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, and that revert-warring over optional styles is unacceptable. If discussion cannot determine which style to use in an article, defer to the style used by the first major contributor.

General notes

Quotations, titles, etc.

See also: WP:MOSQUOTE

Quotations, titles of books and articles, and similar "imported" text should be faithfully reproduced, even if they employ 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.

• It is acceptable to change other date formats in the same article to provide consistency, so long as those changes would otherwise be acceptable.

Non-breaking spaces

Guidance on the use of non-breaking spaces is contained in some of the sections below. For further information see Wikipedia:Manual of Style#Non-breaking spaces and Wikipedia:Line-break handling.

Chronological items

Statements likely to become outdated

See also: Wikipedia:As of and Wikipedia:Manual of Style/Words to watch § Relative time references

Except on pages which are updated regularly (e.g. current events), avoid statements that are likely to become quickly outdated. Avoid words such as now, soon or in modern times (unless their intended meaning is clear), currently and recently (except on rare occasions where they are not redundant), or phrases such as the sixties. Instead, use more precise phrases such as during the 1990s or in August 1969. For future and current events, use phrases such as as of December 2024 or since the beginning of 2010 to signal the time-dependence of the information. (It may be useful to re-read a passage from the perspective of a reader five years in the future.)

Relative-time expressions are acceptable for very long periods, such as geological epochs: Our ancestors are believed to have diverged from the other great apes long ago, but only recently developed the use of fire.

To help editors keep information up to date, statements about current and future events may be used with the as of technique, which uses the {{as of}} template to tag information that may become dated quickly: {{as of|2024}} produces the text As of 2024 and categorises the article appropriately. This technique is not an alternative to using precise language. For instance, one should not replace since the start of 2005 with {{as of|2005}} because some information (the start of 2005) would be lost; instead, use either the plain text or a more advanced feature of {{as of}} such as {{as of|2005|alt=since the start of 2005}}.

Time of day

Context determines whether the 12- or 24-hour clock is used; in both, colons separate hours, minutes and seconds (e.g. 1:38:09 pm or 13:38:09).

• 12-hour clock times end with dotted or undotted lower-case a.m. or p.m., or am or pm, preceded by a space (e.g. 2:30 p.m. or 2:30 pm, not 2:30p.m. or 2:30pm). Hours denoted by a single digit should not have a leading zero (e.g. 2:30 p.m., not 02:30 p.m.). A hard space (see above) is advisable (2:30 pm or {{nowrap|2:30 p.m.}}). Use noon and midnight rather than 12 pm and 12 am; whether midnight refers to the start or the end of a date will need to be specified unless it is clear from the context.
• 24-hour clock times have no a.m., p.m., noon or midnight suffix. Hours under 10 should have a leading zero (e.g. 08:15). 00:00 refers to midnight at the start of a date, 12:00 to noon, and 24:00 to midnight at the end of a date, but should not be used for the first hour of the next day (e.g. use 00:10 for ten minutes after midnight, not 24:10).

Time of day is normally expressed in figures rather than being spelled out. For details, and information on time intervals (e.g. 5 minutes), see Numbers as figures or words, below.

Time zones

When giving a date, consider where the event happened and use the time zone there. For example, the date of the attack on Pearl Harbor should be December 7, 1941 (Hawaii time/date). In judging where, give priority to the place at which the event had its most significant effects; for example, if a hacker based in Japan 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 give the date and time in Coordinated Universal Time (UTC). For example:

8 p.m. Eastern Standard Time on January 15, 2001 (01:00 UTC, January 16)

Alternatively, just include the UTC offset:

21:00 British Summer Time (UTC+1) on 27 July 2012

Rarely, the time zone in which a historical event took place has changed since that epoch; for example, China under the Republic was divided into five time zones (see Historical time zones of China) while all of modern China is UTC+8. Similarly, the term "UTC" is not appropriate for dates before this system was adopted in 1961; 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 may differ.

Dates and years

Formats

Date formats

Acceptable date formats

General use	Only where brevity is required (references, tables, lists, etc.)	Notes
22 August 2001	22 Aug 2001
August 22, 2001	Aug 22, 2001	A comma follows the year unless followed by other punctuation: The weather on September 11, 2001, was clear and warm Everyone remembers July 21, 1969‍—‌when man landed on the Moon
22 August	22 Aug	Omit year only where there is no risk of ambiguity: In 2013, Ramadan began on 10 July and ended on 7 August January 1 is New Year's Day
August 22	Aug 22
No equivalent for general use	2001-08-22	Use only with Gregorian dates between 1583 and 9999

• For issues related to dates in sortable tables, see Date sorting problems or consider using {{sort|2008-11-01|1 Nov 2008}} or {{dts|Nov 1, 2008}}.
• Phrases such as Fourth of July (or July Fourth, but not July 4th), Cinco de Mayo, Seventh of March Speech and Sete de Setembro are proper names, to which rules for dates do not apply (Every Fourth of July celebration includes fireworks)

Unacceptable date formats (except in external titles and quotes)

	Unacceptable	Acceptable
Do not use 1st, 2nd, 3rd, etc.	June 9th 9th June the 9th of June	9 June or June 9
Do not add a dot to the day	9. June
Do not "zero-pad" month and day, except in all-numeric (yyyy-mm-dd) format	09 June June 09
	2005-4-8	2005-04-08
Do not use separators other than hyphen	2005/04/08
Do not use dd-mm-yyyy or mm-dd-yyyy as they are ambiguous	03-04-2007 04-03-2007	???
Do not use these formats	2001 July July of 2001	July 2001
No comma between month and year	July, 2001
	3 July, 2001	3 July 2001
Comma required between day and year	July 3 2001	July 3, 2001
Do not use an apostrophe to abbreviate year	the '02 elections	the 2002 elections
Roman numerals are not normally used for dates	Copyright MMII	Copyright 2002
Years and days of the month are not normally written in words	Two thousand one the first of May	2001 May 1 or 1 May
Use "in the year" only where needed for clarity (About 1800 ships arrived in the year 1801)	sold in the year 1995	sold in 1995

Consistency

• Dates in article body text should all use the same format: Julia ate a poisoned apple on 25 June 2005, and died on 28 June (not ... on June 28).
• Publication dates in references should all use use the same format. Any format from the "Acceptable date formats" table above may be used, unless the citation style being used requires a different format (however, all-numeric date formats other than yyyy-mm-dd must still be avoided). For example, in a single article write:

Jones, J. (20 Sep 2008)

Smith, J. (Sep 2002)

but not:

Jones, J. (20 Sep 2008)

Smith, J. (September 2002)

• Access and archive dates in references should all use the same format – either the format used for publication dates, or yyyy-mm-dd:

Jones, J. (20 Sep 2008) ... Retrieved 5 Feb 2009.

Jones, J. (20 Sep 2008) ... Retrieved 2009-02-05.

but not:

Jones, J. (20 Sep 2008) ... Retrieved 5 February 2009.

Jones, J. (20 Sep 2008) ... Retrieved Feb 5, 2009.

Jones, J. (20 Sep 2008) ... Retrieved February 5, 2009.

See: {{Use dmy dates}}, {{Use mdy dates}}

Strong national ties to a topic

See also: Wikipedia:Manual of Style: Strong national ties to a topic

• Articles on topics with strong ties to a particular English-speaking country should generally use the more common date format for that nation. For the United States, this is month before day; for most others, it is day before month. Articles related to Canada may use either format consistently.
• Sometimes the customary format differs from the usual national one: for example, articles on the modern US military use day before month, in accordance with military usage.

Retaining existing format

See also: Wikipedia:Manual of Style: Retaining the existing variety

• If an article has evolved using predominantly one format, the whole article should conform to it, unless there are reasons for changing it based on strong national ties to the topic or consensus on article talk.
• The date format chosen by the first major contributor in the early stages of an article should continue to be used, unless there is reason to change it based on strong national ties to the topic or consensus on article talk.
• 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 era is the Western Dionysian era system, a year numbering system also known as the Western Christian era (represented by BC and AD), or the Common Era (represented by BCE and CE).
  • BC and AD are the traditional ways of referring to this era. BCE and CE are common in some scholarly texts and religious writings. Either convention may be appropriate.
    • Do not change the established era style in an article unless there are reasons specific to its content. Seek consensus on the talk page before making the change. Open the discussion under a subhead that uses the word "era". Briefly state why the style is inappropriate for the article in question. A personal or categorical preference for one era style over the other is not justification for making a change.
    • BCE and CE or BC and AD are written in upper case, unspaced, without periods (full stops), and separated from the year number by a space (5 BC, not 5BC). It is advisable to use a non-breaking space.
    • AD may appear before or after a year (AD 106, 106 AD); the other abbreviations appear after (106 CE, 3700 BCE, 3700 BC).
    • Do not use CE or AD unless the date or century would be ambiguous without it (e.g. "The Norman Conquest took place in 1066" not 1066 CE nor AD 1066). On the other hand, "Plotinus was a philosopher living at the end of the 3rd century AD" will avoid unnecessary confusion. Also, in "He did not become king until 55 CE" the era marker makes it clear that "55" does not refer to his age. Alternatively, "He did not become king until the year 55."
    • Use either the BC–AD or the BCE–CE notation consistently within the same article. Exception: do not change direct quotations.
• Uncalibrated (bce) radiocarbon dates: Some source materials will indicate whether a date is calibrated or not simply by a change in capitalisation; this is often a source of confusion for the unwary reader. Do not give uncalibrated radiocarbon dates (represented by the lower-case bce unit, occasionally bc or b.c. in some sources), except in directly quoted material, and even then include a footnote, a square-bracketed editor's note [like this], or other indication to the reader what the calibrated date is, or at least that the date is uncalibrated. Calibrated and uncalibrated dates can diverge surprisingly widely, and the average reader does not recognise the distinction between bce and BCE / BC.
• BP: In scientific and academic contexts, BP (before present) is often used. This is calibrated from January 1, 1950, not from the date of publication, though the latter introduces an insignificant error when the date is distant or an approximation (18,000 BP). BP years are given as 18,000 BP or spelled out as 18,000 years before present (not 18,000 YBP, 18,000 before present, 18,000 years before the present, or similar.) Do not convert other notations to or from BP unless you are certain of what you are doing. A safer and less complex alternative may be to just use "ya (years ago)".
• Other era systems may be appropriate in an article. In such cases, dates should be followed by a conversion to Dionysian (or vice versa) and the first instance should be linked: "Qasr-al-Khalifa was built in 221 AH (836 CE)" or "in 836 AD (221 AH)".
  • Astronomical year numbering follows the Common Era and does not require conversion, but the first instance of a non-positive year should still be linked: "The March equinox passed into Pisces in year −67."

Julian and Gregorian calendars

See also: Old Style and New Style dates

Dates can be given in any appropriate calendar, as long as the date in either the Julian or Gregorian calendars is provided, 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, this must be clear to readers.

• Current events are given in the Gregorian calendar.
• Dates before the adoption of the Gregorian calendar on 15 October 1582 are normally given in the Julian calendar. The Julian day and month should not be converted to the Gregorian calendar, but the start of the Julian year should be assumed to be 1 January (see below for more details).
• Dates for Roman history before 45 BC are given in the Roman calendar, which was neither Julian nor Gregorian. When (rarely) the Julian equivalent is certain, it may be included.
• The Julian or Gregorian equivalent of dates in early Egyptian and Mesopotamian history is often debatable. Follow the consensus of reliable sources, or indicate their divergence.
• Dates of events in countries using the Gregorian calendar are given in the Gregorian calendar. This includes some of the Continent of Europe from 1582, the British Empire from 14 September 1752, and Russia from 14 February 1918 (see the Gregorian calendar article).

The dating method used should follow that used by reliable secondary sources. If the reliable secondary sources disagree, choose the most common used by reliable secondary sources and note the usage in a footnote.

At some places and times, dates other than 1 January were used as the start of the year. The most common English-language convention was the Annunciation Style used in Britain and its colonies until 1752, in which the year started on 25 March, Annunciation Day; see the New Year article for a list of other styles. 1 January is assumed to be the opening date for years; if there is reason to use another start-date, this should be noted.

If there is a need to mention Old Style or New Style dates in an article (as in the Glorious Revolution), a footnote should be provided on the first usage, stating whether the New Style refers to a start of year adjustment or to the Gregorian calendar (it can mean either).

Ranges

• A pure year–year range is written (as is any range) using an en dash (– or {{ndash}}), not a hyphen or slash; this dash is usually unspaced (that is, with no space on either side); and the range's "end" year is usually abbreviated to two digits:

1881–86;  1881–92 (not 1881–6;  1881 – 86)

Markup: 1881{{ndash}}86 or 1881–86

But both years are given in full in the following cases:

• birth–death parentheticals: Petrarch (1304–1374) was ...;  not (1304–74)
• different centuries: 1881–1903;  not 1881–03
• starting year before 1000 AD: 355–372 (not 355–72);  95–113;  95–113 AD;  982–1066;  2590–2550 BCE;  1011–922 BC

Markup: 355{{ndash}}372{{nbsp}}AD

• spanning from BC/BCE to AD/CE: 42 BC – 15 AD (note spaced en dash)

Markup: 42{{nbsp}}BC{{snd}}15{{nbsp}}AD or 42 BC – 15 AD

Other notes:

• 2005–06 generally denotes a two-year range
• 2005/06 may be used to signify a fiscal year or other special period, if that convention is used in reliable sources
• Sports seasons straddling January 1 should be uniformly written as 2005–06 season. A range of sports seasons in an infobox may also be written as 2005–2010.

• Other "pure" ranges use an unspaced en dash as well:

• day–day: 5–7 January 1979;  January 5–7, 1979;  elections were held March 5–8
• month–month: June–August 1940;  the May–September peak season

• If either or both endpoints are in a "mixed" format (containing two or more of month, day, year) a spaced en dash is used:

• between days in different months: They travelled June 3 – August 18, 1952;  They travelled 3 June – 18 August 1952
• between dates in different years:

Charles Robert Darwin (12 February 1809 – 19 April 1882) was an English naturalist ...

Markup: 12{{nbsp}}February 1809{{snd}}19{{nbsp}}April 1882 or 12 February 1809 – 19 April 1882

Abraham Lincoln (February 12, 1809 – April 15, 1865) was the 16th President of ...

• between months in different years: The exception was in force August 1892 – January 1903;  The Ghent Incursion (March 1822 – January 1, 1823) was ended by the New Year's Treaty

Markup: March 1822{{snd}}January{{nbsp}}1, 1823 or March 1822 – January 1, 1823

• For a person still living: Serena Williams (born September 26, 1981) ..., not (September 26, 1981–) or (born on September 26, 1981)
• An overnight period may be expressed using a slash between two contiguous dates: the night raids of 30/31 May 1942 or raids of 31 May / 1 June 1942.

Or use an en dash: raids of 30–31 May 1942;  raids of 31 May – 1 June 1942.

• Express a time period either using a dash, or using a word such as from or between, but not both: from 1881 to 1886 (not from 1881–86);  between February 1 and March 3 (not between February 1 – March 3)

In biographical infobox templates, it is good practice to use date mathematics templates for age calculation, so as to provide microformat compatibility.Wikipedia:Manual of Style/Biographies for more guidelines on articles about people.

Uncertain, incomplete, or approximate dates

• To indicate around, approximately, or about, use of the spaced, unitalicised form c. 1291 (or the {{circa}} template) is preferred over circa, ca, ca., approximately, or approx.:

At the birth of Roger Bacon (c. 1214) ...

John Sayer (c. 1750 – 2 October 1818) ...

the Igehalkid dynasty of Elam, c. 1400 BC ...

• Where both endpoints of a range are approximate, c. should be appear before each date:

Dionysius Exiguus (c. 470 – c. 540) ... (not Dionysius Exiguus (c. 470 – 540) ...)

Rameses III (reigned c. 1180 – c. 1150 BCE) ... (not Rameses III (reigned c. 1180 – 1150 BCE) ...)

• Where birth/death dates have been extrapolated from known dates of activity:

Offa of Mercia (before 734 – 26 July 796) ...

Robert Menli Lyon (1789 – after 1863) ...

Ambrose Gwinnett Bierce (June 24, 1842 – after December 26, 1913) ...

• When a person is known to have been active ("flourishing") during certain years, fl., [[floruit|fl.]], or {{fl.}} may be used:

Osmund (fl. 760–772) ...

Aethelwalh (fl. c. 660 – 685) ...

The linked forms should not be used on disambiguation pages, and "active" followed by the range is a better alternative for artists, soldiers and other persons with an occupation.

• 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):

Anne Smith (born 1912 or 1913; died 2013) ...

• Other forms of uncertainty should be expressed in words, either in article text or in a footnote: April 14, 1224 (unattested date). Do not use a question mark (1291?) for such purposes, as this fails to communicate the nature of the uncertainty.

Linking and autoformatting of dates

It is no longer recommended to link dates purely for the purpose of autoformatting. Dates should only be linked when they are germane and topical to the subject, as discussed at Wikipedia:Linking#Chronological items.

Other periods

• Day, month and season names: See Wikipedia:Manual of Style/Capital letters#Calendar items

• Months are expressed as whole words (February, not 2), except in the YYYY-MM-DD format (e.g. 2001-05-03). (Note: YYYY-MM format, such as 2001-03 to represent March 2001, is not acceptable due to potential confusion with e.g. the year range 2001–2003). Unlike some other languages, the names of months and days of the week are capitalised in English. Abbreviations such as Feb. in the United States or Feb in most other countries are used only where space is extremely limited, such as in tables and infoboxes. Do not insert of, or a comma, between a month and a year (April 2000, not April of 2000 or April, 2000).

• Seasons. The names of the seasons should only be used when referring to seasonal occurrences. As the seasons are reversed in the northern and southern hemispheres—and areas near the equator tend to have just wet and dry seasons—it is usually preferable to use neutral wording to refer to times of the year (in early 1990, in the second quarter of 2003, around September, rather than summer 1918 or spring 1995). Even when the season reference is unambiguous (as when a particular location is clearly involved) a date or month may be preferable to a season name. Seasons may be used when there is a logical connection to the event they are describing (the autumn harvest) or when referring to a phase of a natural yearly cycle (migration to higher latitudes typically starts in mid-spring).

• Decades
  • Decades as such contain neither an apostrophe nor the suffix -ies (the 1980s, not the 1980's, not the 1980-ies, and definitely not the 1980s'). The two-digit form is never used in reference to the decade as a time span per se.
  • The two-digit form, to which a preceding apostrophe should be added, is used only in reference to a social era or cultural phenomenon that roughly corresponds to and is said to define a decade, and only if it is used in a sourceable stock phrase (the Roaring '20s, the Gay '90s), or when there is a notable connection between the period and what is being discussed in the sentence (a sense of social justice informed by '60s counterculture, but grew up in 1960s Boston, moving to Dallas in 1971). Such an abbreviation should not be used if it would be redundant ('80s Reaganomics) or if it does not have a clear cultural significance and usage (the '10s).

• Centuries and millennia
  • For purposes of written style, the English Wikipedia does not recognise a year 0. Therefore, for dates AD (or CE) the 1st century was 1–100, the 17th century was 1601–1700, and the second millennium was 1001–2000; for dates BC (or BCE) the 1st century was 100–1; the 17th century was 1700–1601, and the second millennium was 2000–1001.
  • Centuries and millennia not in quotes or titles should be either spelled out (eighth century) or in Arabic numeral(s) (8th century). The same style should be used throughout any article.
  • Forms such as the 1700s are normally best avoided since it may be unclear whether a 10- or 100-year period is meant (i.e. 1700–1709 or 1700–1799).
  • Remember that the 18th century (1701–1800) and the 1700s (1700–1799) do not span the exact same period.

• Abbreviations for long periods of time: When the term is frequent, combine the abbreviations yr for "years" and ya for "years ago" with prefixes k for "thousand" (kya, kyr), m for "million" (mya, myr), and b for "billion" (bya, byr). In academic contexts, annum-based units are often used: ka (kiloannum), Ma (megaannum) and Ga (gigaannum). Some authorities, such as the British Museum, simply spell out "years ago". For any abbreviation, show the meaning of the unit parenthetically on first occurrence and again where use is extensive, or might be a standalone topic of interest. For source quotations use brackets, as in "a measured Libby radiocarbon date of 35.1 mya [million years ago] had to be calibrated ..."

Numbers

Numbers as figures or words

Generally, in article text:

• Integers from zero to nine are spelled out in words
• Integers greater than nine expressible in one or two words may be expressed either in numerals or in words (16 or sixteen, 84 or eighty-four, 200 or two hundred). In spelling out numbers, "components" from 21 to 99 are hyphenated; larger ones are not:

  •  fifty-six

  •  five hundred

  •  four hundred seven

  •  two thousand four hundred sixty-six

• Other numbers, such as ordinal (indicating sequential order) and cardinal numbers (indicating quantity), are given in numerals (3.75, 544) or in forms such as 21 million or 1.6 billion. Markup: 21{{nbsp}}million or 1.6{{nbsp}}billion

Notes and exceptions:

• In tables and infoboxes quantities are expressed in figures (Years in office: 5); but numbers within a table's explanatory text and comments follow the general rule.
• Fractions:
  • Spelled-out fractions are hyphenated: seven-eighths.
  • Common fractions for which the numerator and denominator can be expressed in one word are usually spelled out, e.g. a two-thirds majority; use figures if they occur with an abbreviated unit, e.g. 1⁄4 yd and not a quarter of a yd.
  • Mixed fractions are usually expressed in figures, e.g. 2+1⁄4; however, the fractional part should always be consistent with the integral part, e.g. Nine and a half, and not Nine and 1⁄2.
  • Percentages are usually written with figures, e.g. 10 percent or 10%.
• Numbers in mathematical formulae are never spelled out (3 < π < 22/7, not three < π < 22 sevenths).
• Comparable quantities should be all spelled out or all figures:

  •  five cats and thirty-two dogs, not five cats and 32 dogs.

  •  86 men and 103 women not eighty-six men and 103 women

  •  There were 3 deaths and 206 injuries or Three died and two hundred six were injured, not There were three deaths and 206 injuries

• But adjacent quantities that are not comparable should usually be in different formats: twelve 90-minute volumes or 12 ninety-minute volumes, not 12 90-minute volumes or twelve ninety-minute volumes.
• The numerical elements of times-of-day are not normally spelled out (twelve forty-five p.m.) though conventional terms such as noon and midnight are acceptable (taking care, with the latter, to avoid possible date ambiguity in constructions such as midnight on July 17).
• Centuries are given in figures or words using adjectival hyphenation where appropriate: the 5th century BCE; nineteenth-century painting. Neither the ordinal nor the word "century" should be capitalised.
• Do not spell numbers out before symbols for units of measurement: write five minutes, 5 minutes, or 5 min, but not five min.
• Measurements, stock prices, and other quasi-continuous quantities are normally stated in figures, even when the value is a small positive integer: 9 mm, The option price fell to 5 within three hours after the announcement.
• Ages are typically stated in figures, unless it is a large, approximate quantity: an 8-year-old child, the 69-million-year-old fossil.
• When expressing large approximate quantities, it is preferable to write them spelled out, or partly in figures and part as a spelled‑out named number; e.g. one hundred thousand troops may be preferable to 100,000 troops when the size of the force is not known exactly; write Japan has the world's tenth largest population, with about 128 million people (as it is just an approximation to a number likely to be anywhere between 127,500,000 and 128,500,000), but The movie grossed $28,106,731 on its opening day (the exact quantity).
• Sometimes, the variety of English used in an article may call for the use of a numbering system other than the Western thousands-based system. For example, the South Asian numbering system is conventionally used in South Asian English. In those situations, 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.) Also, provide a conversion to Western numbers for the first instance of each quantity, and provide conversions for subsequent instances if they do not overwhelm the content of the article. For example, write three crore (thirty million). Group digits in Western thousands-based style (e.g., 30,000,000; not 3,00,00,000): see Delimiting (grouping of digits) below. (Note that the variety of English does not uniquely determine the method of numbering in an article. Other considerations, such as conventions used in mathematics, science and engineering, may also apply, and the choice and order of formats and conversions is a matter of editorial discretion and consensus.)
• Sometimes figures and words may carry different meanings, for example Every number except one implies that there is one exception (we don't know which), while Every number except 1 means that the specific number 1 is the exception.
• A sentence never begins with figures:

Not There were many attacks. 23 men were killed. but There were many attacks, and 23 men were killed. or There were many attacks. Twenty-three men were killed.

Not 1945 and 1950 saw important elections (nor Nineteen forty-five and 1950 saw important elections – because comparable numbers should be both written in words or both in figures) but The elections of 1945 and 1950 were important.

• Proper names, formal numerical designations, and other idioms comply with common usage; e.g. write Chanel No. 5, 4 Main Street, 1-Naphthylamine, Channel 6, Fourth Amendment, Seventeenth Judicial District, Seven Years' War. This is the case even where it causes a numeral to open a sentence, although this is usually avoided by rewording.

Typography

• Where a whole number in a percentage is spelled out, the percent sign is not used (three percent, not three %).
• The ordinal suffix (st, nd, rd, or th) is not superscripted (123rd and 496th, not 123^rd and 496^th).
• The dot (.) or ordinal mark (º) should not be used as an ordinal suffix, except in direct quotations.

Delimiting (grouping of digits)

• Numbers with five or more digits to the left of the decimal point (i.e. 10,000 or greater) should be delimited into groups so they can be easily parsed, such as by using a comma (,) every three digits (e.g. 12,200, 255,200, 8,274,527). A full stop (.) should not be used to separate thousands (e.g. 12.200, 255.200) to avoid confusion with the decimal point.
• Numbers with four digits to the left of the decimal point may or may not be delimited (e.g. 1250 or 1,250).
• Numbers are not delimited when they are part of mailing and shipping addresses, page numbers, or years with four or fewer digits; years with five or more digits should be delimited (e.g. 10,400 BC).
• In scientific articles, particularly those directed to an expert readership, numbers may be delimited with thin spaces using the {{gaps}} template: {{gaps|8|274|527}} produces 8274527 (note: the thin space character and its HTML entity,  , do not render correctly on some browsers or on screen readers used by visually impaired people).
• Numbers with more than four digits to the right of the decimal point, particularly those in engineering and science where distinctions between different values are important, may be separated (delimited) into groups using the {{val}} template, which uses character-positioning techniques rather than distinct characters to form groups. According to ISO convention (observed by the NIST and the BIPM), it is customary to not leave a single digit at the end, so the last group comprises two, three, or four digits: 1.123, 1.1234, 1.12345, 1.123456, 1.1234567, 1.12345678, 1.123456789, etc. The {{val}} template handles these grouping details automatically; e.g. {{val|1.1234567}} generates 1.1234567 (with a four-digit group at the end), but it can parse no more than a total of 15 significant digits in the significand. For significands longer than this, delimit high-precision values using the {{gaps}} template; e.g. {{gaps|1.234|567|890|123|456}} → 1.234567890123456.
• Constants in mathematics-oriented articles may be grouped in fives; e.g. 3.141592653589793238462643383279....
• The style of delimiting numbers must be consistent throughout an article.

Large numbers

See also: Order of magnitude and Long and short scales

• Large round numbers are generally assumed to be approximations; only where the approximation could be misleading is it necessary to qualify with words such as about.
• Avoid excessively precise values where they are unlikely to be stable or accurate, or where the precision is unnecessary in the context. The sentence The speed of light in a vacuum is 299,792,458 metres per second may well be appropriate since it is precisely that value; The distance from the Earth to the Sun is 149,014,769 kilometres and The population of Cape Town is 2,968,790 are not appropriate, because neither value is stable at that level of precision. The template {{undue precision}} can be used to tag such figures.
• Scientific notation (e.g. 5.8×10⁷ kg) is preferred in scientific contexts; editors can use the {{val}} template, which generates such expressions with the syntax {{val|5.8|e=7|u=kg}}.
• Where values in the millions occur a number of times through an article, upper-case M may be used for million, unspaced, after spelling out the first occurrence (e.g. She bequeathed her fortune of £100 million unequally: her eldest daughter received £70M, her husband £18M, and her three sons £4M each.).
• The named numbers billion and trillion are understood to be short scale, 10⁹ and 10¹² respectively (see Long and short scales). After the first occurrence in an article, billion may be abbreviated to unspaced bn ($35bn). The prefixes giga-, tera-, and larger and their symbols G, T, ... should be limited to computing and scientific contexts.

Minus sign

Unary minus sign (−) may constitute a part of numeral. This is the case for negative numbers (−17) and also, for small numbers in the scientific notation, in exponent (10⁻¹²). The use of hyphen-minuses (-) instead of proper minus signs has several disadvantages and should be avoided. Keyboard-friendly notations such as -17, 10^-12 or mol^-1 can suddenly appear wrapped in a browser window, making the quantity unreadable.

The unary minus sign can be produced with the − markup code.

There should be no space between a unary "−" and the numeral, for negative numbers, whereas the sign for the binary operation of subtraction does require a space: x − y = 1 and x = −1 are correct, but x = − 1 is incorrect.

Fractions

• The templates {{frac}} (e.g. 81⁄2) and {{sfrac}} (e.g. 8⁠1/2⁠) are available for representing common fractions.
• Mixed numbers are unspaced:

• Correct: A History of the World in 101⁄2 Chapters is a novel by Julian Barnes.
• Incorrect: A History of the World in 10 1⁄2 Chapters is a novel by Julian Barnes.

• Unless there is sound reason to the contrary, fractional parts of metric units should be expressed as decimal fractions (5.25 mm), not vulgar fractions (51⁄4 mm). However Imperial, English, avoirdupois, and United States customary units may use either form – both (5.25 inches) and (51⁄4 inches) are acceptable, provided that there is consistency in the way that the fractions are represented.
• In science and mathematics articles, fractions should always be written either with a horizontal fraction bar (as in $\textstyle {\frac {1}{2}}$ or ⁠1/2⁠), or with a forward slash and with the baseline of the numbers aligned with the baseline of the surrounding text (as in 1/2). The use of {{frac}} (such as 1⁄2) is discouraged in these articles.
• The use of the few Unicode symbols available for fractions (such as ½) is discouraged entirely, for accessibility reasons among others.
• Use of the ordinal suffix (e.g. th) with fractions expressed in figures is discouraged (e.g. 1/100, not 1/100th).

Decimal points

• A decimal point is used between the integer and the fractional parts of a decimal; a comma is never used in this role (6.57, not 6,57).
• The number of decimal places should be consistent within a list or context (The response rates were 41.0 and 47.4 percent, respectively, not The response rates were 41 and 47.4 percent, respectively), except if the quantities were measured with different precisions.
• Numbers between −1 and +1 require a leading zero (0.02, not .02); exceptions are sporting performance averages (.430 batting average) and commonly used terms such as .22 caliber.

Percentages

• Percentages are usually written with figures—e.g., 10 percent or 10%.
• Percent (American English) or per cent (British English) is commonly used to indicate percentages in the body of an article. The symbol % is more common in scientific or technical articles and in complex listings.
• The symbol is unspaced (71%, not 71 %).
• In tables and infoboxes, the symbol % is normally preferred to the spelled-out percent or per cent.
• Ranges should be formatted with one rather than two percentage signifiers (22–28%, not 22%–28%).
• Avoid ambiguity in expressing a change of rates. This can be done by using percentage points, not percentages, to express a change in a percentage or the difference between two percentages; for example, The agent raised the commission by five percentage points, from 10 to 15% (if the 10% commission had instead been raised by 5%, the new rate would have been 10.5%). It is often possible to recast the sentence to avoid the ambiguity (raised the commission from 10% to 15%). Percentage point should not be confused with basis point, which is a hundredth of a percentage point.

Repeating decimals

The preferred way to indicate a repeating decimal is to place a bar over the digits that repeat. To achieve this the template {{overline}} can be used. For example, the markup 14.{{overline|285714}} gives 14.285714 and the fraction 328⁄9000 (0.036444…) can be written in decimal form as 0.036{{overline|4}} rendering 0.0364.

Consider a short explanation of this notation (called a vinculum) the first time it is used in an article. Some authors place the repeating digits in parentheses rather than using an overbar (perhaps because overbars are not available in their typesetting environment) but this should be avoided in Wikipedia to avoid confusion with expressing uncertainty.

Non-base-10 notations

For numbers expressed in bases other than base ten:

• In computer-related articles, use the C programming language prefixes 0x (zero-ex) for hexadecimal and 0 (zero) for octal. For binary, use 0b. Consider including a note at the top of the page about these prefixes.
• In all other articles, use subscript notation. For example: 137₉, 241₆, 2A9₁₂, A87D₁₆ (use <sub> and </sub>).
• For base eleven and higher, use whatever symbols are conventional for that base. One quite common convention, especially for base 16, is to use upper-case A–F for digits from 10 through 15 (0x5AB3).

Scientific notation, engineering notation, and uncertainty

Notations

• The template {{val}} can be used to facilitate the generation of scientific notation. It is a flexible tool that allows editors great latitude and must have arguments (each section between the vertical bars) properly entered in order for it to generate output that is compliant with formatting conventions.
• Scientific notation is done in the format of: one leading digit – decimal marker – remaining digits ×10n, where n is the integer that produces a single leading digit.
  • 1.602×10⁻¹⁹ is a proper use of scientific notation.
  • 160.2×10⁻¹⁷ is not a proper use of scientific notation.
• Engineering notation is done in the format of: leading digits – decimal marker – remaining digits ×10n, where n is a multiple of 3. The number of leading digits is not more than three.
  • 132.23×10⁶ is a proper use of engineering notation.
  • 1.3223×10⁸ is not a proper use of engineering notation.
• It is clearer to avoid mixing scientific notation and engineering notation in the same context (do not write A 2.23×10² m² region covered by 234.0×10⁶ grains of sand).
• Use discretion when it comes to using scientific and engineering notation. Not all values need to be written in it.
  • Sometimes it is useful to compare values with the same power of 10 (often in tables) and scientific or engineering notation might not be appropriate.
  • Either notation will distinguish the level of precision in a round number such as 5,000, which may mean 5×10³ (estimated to the nearest thousand), 5.0×10³ (to the nearest hundred), 5.00×10³ (to the nearest ten), or 5.000×10³ (to the unit).

Uncertainty

• Where the degree of uncertainty is not given in the source (or is unimportant for the article's purposes) round to an appropriate number of significant digits. The number of digits presented should usually be conservative; for instance, an estimated number of speakers of a language is unlikely to be accurate beyond two or three digits, even if the source is a census or other formal count reporting far more digits. The {{undue precision}} template may be added to figures which appear to be overprecise.
• Do not use "approximately" with numbers that have simply been rounded, as this is misleading. For example, a measurement of "40 km" would normally be understood to refer to a distance closer to 40 km than to 30 or 50 km (that is, within 40 ± 5 km), while "approximately 40 km" would suggest a greater uncertainty than this, such as 20–60 km.
• Where the uncertainty has been calculated and is relevant, it can be written various ways:

•  (1.534 ± 0.35) ×1023 m	Markup: {{val|1.534|0.35|e=23|u=m}}
•  12.34 m2 ± 5% (not used with scientific notation)	Markup: {{val|12.34|u=m2}}{{nbsp}}{{plusmn}}{{nbsp}}5%
•  15.34 +0.43 −0.23 ×1023 m	Markup: {{val|15.34|+0.43|-0.23|e=23|u=m}}
•  1.604(48) ×10−4 J (value 1.60448×10−4 J, uncertainty in the 48)	Markup: {{val|1.604|(48)|e=-4|u=J}}}}

Units of measurement

Which units to use

Science-related articles

• In science-related articles: generally use only SI units, non-SI units officially accepted for use with the SI, and specialized units that are used in some sciences. US Customary and imperial units are not required.

UK engineering-related articles

• In UK engineering-related articles, including all bridges and tunnels: generally use the system of units that the topic was drawn-up in, whether metric or imperial. Provide conversions where appropriate.
• Road distances and speeds are an exception to this: use imperial units with a metric conversion.

Other articles

For other articles, Wikipedia has adopted a system of writing a "main" quantity followed by a conversion in parentheses (see Unit conversions below).

• In non-science US-related articles: the main quantity is generally expressed in US customary units (97 pounds (44 kg)).
• In non-science and non-engineering UK-related articles: the main quantity is generally expressed in metric units (44 kilograms (97 lb)), but imperial units are still used as the main units in some contexts, including:
  • miles, miles per hour, and fuel consumption in miles per imperial gallon;
  • feet/inches and stones/pounds for personal height and weight;
  • imperial pints for draught beer/cider and bottled milk.
  • hands for horses and most other equines
• All other articles: the main unit is generally an SI unit or a non-SI unit officially accepted for use with the SI.

How to present quantities

• Nominal and defined quantities should be given in the original units first, even if this makes the article inconsistent: for example, When the Republic of Ireland adopted the metric system, the road speed limit in built-up areas was changed from 30 miles per hour (48 km/h) to 50 kilometres per hour (31 mph). (The focus is on the change of units, not on the 3.6% increase.)
• Quantities should be accompanied by a proper citation of the source using a method described at the style guide for citation.
• In cases where the primary units in the article are different from the primary units in the source:
  • Ensure that the precision of the converted quantity in the article is comparable to the precision of the quantity from the source.
  • Consider quoting the source quantity in the citation, particularly when the source only provides one system of units.
  • In some cases it may be useful to avoid this by taking the unit used by the source as primary.

SI standard

• SI units are written according to the SI standard unless otherwise specified in this Manual of Style (dates and numbers). For example see American spelling.
• Non-SI units in tables 6, 7, 8, and 9 of the SI brochure are written according to the SI standard unless otherwise specified in this Manual of Style (dates and numbers). For example see guidance on litre.
• Non-SI units mentioned elsewhere in the SI brochure are written according to the SI standard unless otherwise specified in this Manual of Style (dates and numbers). For example see Percentages.

Unit conversions

Where English-speaking countries use different units for the same quantity, follow the "primary" quantity with a conversion in parentheses. This enables more readers to understand the quantity. Examples: the Mississippi River is 2,320 miles (3,734 km) long; the Murray River is 2,375 kilometres (1,476 mi) long.

• With imperial units which are not also US customary units, double conversions can be useful: The song's second verse reveals that Rosie weighs 19 stone (266 lb; 121 kg).
• 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 (The four-minute mile).
  • When units are part of the subject of a topic—nautical miles in articles about the history of nautical law, SI units in scientific articles, yards in articles about American football—it can be excessive to provide conversions every time a unit occurs. It could be best to note that this topic will use the units (possibly giving the conversion factor to another familiar unit in a parenthetical note or a footnote), and link the first occurrence of each unit but not give a conversion every time it occurs.
• Converted quantity values should use a level of precision similar to that of the source quantity value, so the Moon is 380,000 kilometres (240,000 mi) from Earth, not (236,121 mi). However, small numbers may need to be converted to a greater level of precision where rounding would cause a significant distortion, so one mile (1.6 km), not one mile (2 km).
• Category:Conversion templates can be used to convert and format many common units, including {{convert}}, which includes non-breaking spaces.
• In a direct quotation, always keep the source units.
  • Conversions required for quantities cited within direct quotations should appear within square brackets in the quote.
  • Alternatively, you can annotate an obscure use of units (e.g. five million board feet of lumber) with a footnote that provides conversion in standard modern units, rather than changing the text of the quotation. See the style guide for citation, footnoting and citing sources.

Conversion errors

Conversion errors may occur in general reports, so use the primary sources or the most authoritative sources available. This can help avoid rounding errors, like this: a general report stated that the Eurostar is designed for speeds of "186 mph (299 km/h)". However, the actual design speed was 300 km/h. (The error crept in because the original speed had been converted to 186 mph and then back to km/h.) When common conversion factors are given as quantities, this is a clue that there may be conversion problems. For example, if a number of moons are given estimated diameters in increments of 16 km or 6 miles (implied precision ±0.5 km or mi), it is likely that the estimates in the primary source were in increments of a less-precise 10 miles or 10 km (implied precision ±5 miles or km).

See uncertainty in data above.

Straightforward and accurate conversion may not be possible for loose estimates. For example, if the diameter of a moon is estimated to be 10 miles to within an order of magnitude, any simple conversion to kilometers would introduce a significant loss of accuracy or a gross change in precision. That is because an order-of-magnitude estimate of 10 miles implies a possible range of ≈ 3–30 miles, which would be ≈ 5–50 km. A secondary source will commonly convert such an estimate to a specious 16 km.

Unit names and symbols

Unit names and symbols should follow the practice of reliable sources; the following guidelines may be helpful:

Conventions

• 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 (spelling out the first use – Up to 15 kilograms of emulsifier is used for a batch of 250 kg). Certain unit names (e.g. °C) need never be written in full unless required stylistically: Beginning 1972 the tables were published using degrees Celsius instead of degrees Fahrenheit.
• Where space is limited, such as in tables, infoboxes, parenthetical notes, and mathematical formulas, unit symbols are preferable.
• Units unfamiliar to general readers should be presented as a name-symbol pair: The betatron reached energies of 2.3 megaelectronvolts (MeV) initally, but later achieved 300 MeV.
• Ranges use unspaced en dashes if only one unit symbol is used at the end (e.g. 5.9–6.3 kg), and spaced en dashes if two symbols are used (e.g. 3 μm – 1 mm); ranges in prose can be specified using either unit symbol or unit names, and units can be stated either after both numerical values or after the last (e.g. from 5.9 to 6.3 kilograms, from 5.9 kilograms to 6.3 kilograms, from 5.9 to 6.3 kg and from 5.9 kg to 6.3 kg are all acceptable).
• Length-width-height–type dimensions may use the multiplication sign or by.
  • When the multiplication sign is used, each number should be followed by a unit name or symbol: 1 m × 3 m × 6 m, not 1 × 3 × 6 m or 1 × 3 × 6 m³;  1 m × 3 m × 3 cm
  • With by the unit need be given only once: 1 by 3 by 6 metres or 1 m by 3 m by 6 m
  • The letter x (unspaced) may be used in writing conventional terms such as 4x4.

Unit names

• Unit names are common nouns. Write them in lower case except where: common nouns take a capital; otherwise specified in the SI brochure; otherwise specified in this manual of style.
• When unit names are combined by multiplication, separate them with a hyphen or a space (e.g. newton-metre or newton metre). The plural is formed by pluralising the last unit name (e.g. ten newton-metres).
  • When units of torque or energy are formed by multiplication of a unit of force with a unit of length, distinguish these by putting the force unit first for torque (e.g. newton-metres or pound-feet) and the length unit first for energy (e.g. foot-pounds or foot-pounds force).
• When unit names are combined by division, separate them with per (e.g. meter per second, not meter/second). The plural is formed by pluralising the unit preceding the per (e.g. ten metres per second).
• When they form a compound adjective, values and unit names should be separated by a hyphen: for example, a five-day holiday.

American spelling

American spellings of unit names should be used on pages written in American English. See "Specific units" section.

Unit symbols

• Values and unit symbols are separated by a non-breaking space. The {{nowrap}} template or the   character can be used for this purpose. For example, use 10 m or 29 kg, not 10m or 29kg.
  • Exceptions: Non-alphabetic symbols for degrees, minutes and seconds for angles and coordinates and the percent sign are unspaced (for example, 5° 24′ 21.12″ N for coordinates, 90° for an angle, 47% for a percentage, but 18 °C for a temperature). See also the "Geographical coordinates" section.
• Write unit symbols in upright roman type (e.g., 10 m or 29 kg, not 10 m or 29 kg). Italic type is normally reserved for variables and the like.
• Standard symbols for units are undotted (e.g., m for metre, not m.). Non-standard abbreviations should be dotted.
• Symbols are identical in singular and plural—an s is never appended (e.g., km, in, lb, not kms, ins, lbs).
• When unit symbols are combined by multiplication, use a middle dot (·) or a non-breaking space ( ) to separate the symbols. For example, ms is the symbol for the millisecond, while m·s or m s is the symbol for the metre-second.
• When unit symbols are combined by division, use a slash to separate the symbols (e.g., for the metre per second use the symbol m/s, not mps) or use negative exponents (m·s⁻¹). Exceptions include mph for the mile per hour, psi for pounds per square inch, etc.
  • Follow a slash in a compound unit symbol with exactly one unit symbol, or with a product of units in parentheses; do not use multiple slashes (kg/(m·s), not kg/m/s or kg/m·s).
• Write powers of unit symbols with HTML (e.g., 5&nbsp;km<sup>2</sup> for 5 km²), not Unicode subscripts and superscripts (e.g., 5 km²). HTML superscripts are easier to read.
• The abbreviations sq and cu (e.g., 15 sq mi and 3 cu ft) may be used for US customary and imperial units but not for SI units.
• Unit symbols/abbreviations, apart from those listed below, are written in either non-alphabetic characters or in lower-case letters unless they are derived from a proper name, in which case the first letter is a capital letter. (This applies to the unit itself, not its prefix).
• Do not use the prefixes M for 10³, MM for 10⁶, or B for 10⁹; use SI prefixes instead.

Quantities of bytes and bits

In quantities of bits and bytes, the prefixes kilo (symbol k or K), mega (M), giga (G), tera (T), etc. are ambiguous. They may be based on a decimal system (like the standard SI prefixes), meaning 10³, 10⁶, 10⁹, 10¹², etc., or they 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 k should be used for "kilo-" whenever it means 1000 in computing contexts, whereas a capital 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 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 ({{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 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:

  A 64 MB (64 × 1024² byte) video card and a 100 GB (100 × 1000³ byte) hard drive

  A 64 MB (64 × 2²⁰ byte) video card and a 100 GB (100×10⁹ byte) hard drive

  A 64 MB (67,108,864 byte) video card and a 100 GB (100,000,000,000 byte) hard drive

• Avoid inconsistent combinations such as A 64 MB (67,108,864 byte) video card and a 100 GB (100 × 1000³ byte) hard drive. Footnotes, such as those seen in Power Macintosh 5500, may be used for disambiguation.
• Unless explicitly stated otherwise, one byte is eight bits (see History of byte).

The IEC prefixes kibi-, mebi-, gibi-, etc. (symbols Ki, Mi, Gi, etc.) are rarely used, even in technical articles (see Complete rewrite of Units of Measurements (June 2008)), so are generally not to be used except under the following circumstances:

• when the article is on a topic where the majority of cited sources use the IEC prefixes,
• when directly quoting a source that uses the IEC prefixes,
• in articles specifically about or explicitly discussing the IEC prefixes,
• when an article uses both, binary and decimal units intermixed and no primary usage can be determined with certainty, or converting all other occurrences of units into the primary unit would be misleading or lose necessary precision, or declaring the actual meaning of a unit on each occurrence would be impractical.

Wikipedia follows common practice regarding bytes and other data traditionally quantified using binary prefixes (e.g. mega- and kilo-, meaning 2²⁰ and 2¹⁰ respectively) and their unit symbols (e.g. MB and KB). Despite the IEC's 1998 International Standard creating several new binary prefixes (e.g. mebi-, kibi-) to distinguish the meaning of the decimal SI prefixes (e.g. mega- and kilo-, meaning 10⁶ and 10³ respectively) from the binary ones, and the subsequent incorporation of these IEC prefixes into the International System of Quantities (ISQ), consensus on Wikipedia in computing-related contexts currently favours the retention of the more familiar but ambiguous units "KB", "MB", "GB", "TB", "PB", "EB", etc. over use of unambiguous IEC binary prefixes. Use 256 MB of RAM, not 256 MiB of RAM.

Specific units

The following table sets out selected units with their appropriate symbols and special comments. This is not an exhaustive list of all units that may be used.

Group	Name	Symbol	Comment
Length
	inch	in	Do not use double quote (") or ″.
	foot	ft	Do not use apostrophe/​single quote (') or ′.
	foot per second	ft/s (not fps)
	hand	h or hh	Equivalent to 4 inches (100 mm); used in measurement of horses. A dot followed by additional inches specifies intermediate heights.
	knot	kn (not kt or kN)
	metre meter (U.S.)	m
	micron	μm (not μ)	Markup: μm  Link to micrometre (for which micron is a synonym) on first use.
	mile	mi	In nautical and aeronautical contexts use statute mile rather than mile to avoid confusion with nautical mile.
	mile per hour	mph
nautical mile	nmi or NM (not nm)
Volume	cubic centimetre cubic centimeter (U.S.)	cm3	Markup: cm<sup>3</sup>
		cc	Non-SI symbol used for certain engine displacements; link to cubic centimetre on first use.
	imperial fluid ounce	imp fl oz	US or imperial/imp must be specified; fluid/fl must be specified (except with gallon).
	imperial fluid pint	imp fl pt
	imperial fluid quart	imp fl qt
	imperial gallon	imp gal
	US fluid ounce	US fl oz
	US fluid pint	US fl pt
	US fluid quart	US fl qt
	US gallon	US gal
	cubic foot	cu ft (not cf)	Write five million cu ft or 5,000,000 cu ft, not 5 MCF.
	cubic foot per second	cu ft/s (not cfs)
	litre liter (U.S.)	l or L	The symbol l in isolation (i.e. not in such forms as ml) is easily mistaken for the digit 1.
Mass
	carat	carat	The metric carat, 200 mg (0.007055 oz), is used for measurement of gemstones and pearls.
	long ton	long ton	Spell out in full.
	short ton	short ton
	pound per square inch	psi
	tonne metric ton (U.S.)	t (not mt or MT)
	troy ounce	ozt	t or troy must be specified. Articles about precious metals, black powder, and gemstones should always specify whether ounces and pounds are avoirdupois or troy.
	troy pound	????
Time
	second	s	Do no use &prime;, &Prime;, or apostrophe/​quotes (' or "). In writing minute-second durations (e.g. for athletic records or album tracks) use a colon (Phineas J. Whoopee was the first to break the four-minute barrier for the Triple-Slalom Skilaufenunterschneigelzumdraus, with a time of 3:58).
	minute	min
	hour	h
	year	a	Only with an SI prefix (a formation 540 Ma old)
Information	bit	bit (not b or B)
	byte	B or byte (not b or o)
	bit per second	bit/s (not bps)
	byte per second	kB/s or kbyte/s (not kBps or KBps)
Angle
	arcminute	′	Markup: &prime;  (not apostrophe/​single quote '). No space between numerals and symbol (47′, not 47 ′)
	arcsecond	″	Markup: &Prime;  (not double-quote "). No space between numerals and symbol (22″, not 22 ″)
	degree	°	Markup: &deg;  (not masculine ordinal º or ring ̊ ). No space between numerals and symbol (23°, not 23 °)
Temperature	degree	°	Markup: &deg;. Nonbreaking space ({{nbsp}}) between numerals and symbol (40 °, not 40°; 12 °C, not 12°C)
	degree Celsius (not degree centigrade)	°C (not C)
Purity
	carat or karat	k or Kt	A measure of purity for gold alloys
Energy	gram calorie small calorie	cal	In science and technology, calorie (used alone) usually refers to the gram calorie, while in dietetics, calorie may refer to the kilogram calorie. Articles should specify either gram calorie (or small calorie) or kilogram calorie (or large calorie), at least on first use. Providing a conversion to SI units is also useful (usually converting gram calories to joules and kilogram calories to kilojoules). A kilogram calorie is equivalent to 1000 gram calories, and is therefore also called a kilocalorie (kilocal); other SI prefixes may be used with the gram calorie (megacal) but not with the kilogram calorie (kiloCal or megaCal).
	kilogram calorie large calorie (not Calorie)	Cal

Currencies

See also: Wikipedia:WikiProject Numismatics/Style § Article titles

Choice of currency

• In country-specific articles, such as Economy of Australia, use the currency of the country.
• In non-country-specific articles such as Wealth, use US dollars ($123), euros (€123), or pounds sterling (£123).

Formatting

• Use the full abbreviation of a currency on its first appearance (e.g. A$52); subsequent occurrences can use just the symbol of the currency (e.g. $88), unless this would be unclear. The exception to this is in articles related entirely to EU-, UK- or US-related topics, in which the first occurrence may also be shortened (€26, £22 or $34 respectively), unless this would be unclear. When there are different currencies using the same symbol in an article, use the full abbreviation (e.g. US$ for the US dollar and A$ for the Australian dollar, rather than just $), unless the currency which is meant is clear from the context.
• Do not place a currency symbol after the value (e.g. 123$, 123£, 123€), unless the symbol is normally written as such. Do not write $US123 or $123 (US).
• Currency abbreviations that come before the number are unspaced if they consist of or end in a symbol (£123, €123), and spaced if alphabetic (R 75).
• If there is no common English abbreviation or symbol, use the ISO 4217 standard.
• Format ranges with one, rather than two, currency signifiers ($250–300, not $250–$300).
• Conversions of less familiar currencies may be provided in terms of more familiar currencies, such as the US dollar, euro or pound sterling using an appropriately chosen rate – this is often not the most recent exchange rate. Conversions should be in parentheses after the original currency, rounding to avoid excess or false precision (one or two significant digits are usually enough, as the exchange rates can vary significantly), with at least the year given as a rough point of conversion rate reference; e.g. Since 2001 the grant has been 10,000,000 Swedish kronor (US$1.4M, €1.0M, or £800k as of August 2009), not (US$1,390,570, €971,673 or £848,646).
• For obsolete currencies, provide if possible an equivalent, formatted as a conversion, in the modern replacement currency (e.g. decimal pounds for historical pre-decimal pounds-and-shillings figures), or at least a US-dollar equivalent as a default in cases where there is no modern equivalent.
• When possible, always link the first occurrence of lesser-known currencies (146 Mongolian tögrögs).
• The names of currencies, currency subdivisions, coins and banknotes should not be capitalised except where normal capitalisation rules require this (for example, at the start of a sentence).
• When called on to use a plural with the euro, use the standard English plurals and not the "legislative" plurals (ten euros and fifty cents, not ten euro and fifty cent). In adjectival use, no plural form is generally used, but rather a hyphenated form: (a two-euro pen, a ten-dollar meal, a ten-cent coin).
• The pound sterling is represented by the £ symbol, with one horizontal bar. The double-barred ₤ symbol is ambiguous, as it has also been used for the Italian lira and other currencies. For non-British currencies that use pounds or a pound symbol (e.g. the Irish pound, IR£) use the symbol conventionally preferred for that currency.

Common mathematical symbols

See also: Wikipedia:Manual of Style/Mathematics.

Common mathematical symbols

Symbol name	Example	Markup	Comments
Plus / positive	x + y	''x'' + ''y''
	+y	+''y''
Minus / negative	x − y	''x'' − ''y''	Do not use hyphen (-) or dashes ({{ndash}} or {{mdash}}).
	−y	−''y''
Plus-minus / minus-plus	41.53 ± 0.35	41.53 ± 0.35
	−(±a) = ∓a	−(±''a'') = ∓''a''
Multiplication, cross	x × y	''x'' × ''y''	The letter x may be used (unspaced) for by in such terms as 4x4.
Division, obelus	x ÷ y	''x'' ÷ ''y''
Equal / equals	x = y	''x'' = ''y''
Not equal	x ≠ y	''x'' ≠ ''y''
Approximately equal	π ≈ 3.14	{{pi}} ≈ 3.14
Less than	x < y	''x'' &lt; ''y''
Less than or equal to	x ≤ y	''x'' &le; ''y''
Greater than	x > y	''x'' &gt; ''y''
Greater than or equal to	x ≥ y	''x'' &ge; ''y''

• Note spaces are placed to left and right of the symbol when used with two operands, but no space with one operand

Geographical coordinates

For draft guidance on, and examples of, coordinates for linear features, see Wikipedia:WikiProject Geographical coordinates/Linear.

Quick guide:

Quick how-to

To add 57°18′22″N 4°27′32″W to the top of an article, use {{Coord}}, thus:

{{Coord|57|18|22|N|4|27|32|W|display=title}}

These coordinates are in degrees, minutes, and seconds of arc.

"title" means that the coordinates will be displayed next to the article's title at the top of the page (in desktop view only; title coordinates do not display in mobile view) and before any other text or images. It also records the coordinates as the primary location of the page's subject in Wikipedia's geosearch API.

To add 44.1124°N 87.9130°W / 44.1124; -87.9130 to the top of an article, use either

{{Coord|44.1124|N|87.9130|W|display=title}}

(which does not require minutes or seconds but does require the user to specify north/ south and east/west) or

{{Coord|44.1124|-87.9130|display=title}}

(in which the north and east are presumed by positive values while the south and west are negative ones). These coordinates are in decimal degrees.

• Degrees, minutes and seconds, when used, must each be separated by a pipe ("|").
• Map datum must be WGS84 if possible (except for off-Earth bodies).
• Avoid excessive precision (0.0001° is <11 m, 1″ is <31 m).
• Maintain consistency of decimal places or minutes/seconds between latitude and longitude.
• Latitude (N/S) must appear before longitude (E/W).

Optional coordinate parameters follow the longitude and are separated by an underscore ("_"):

• dim: dim:N (viewing diameter in metres)
• region: region:R (ISO 3166-1 alpha-2 or ISO 3166-2 code)
• type: type:T (landmark or city(30,000), for example)

Other optional parameters are separated by a pipe ("|"):

• display

  |display=inline (the default) to display in the body of the article only,

  |display=title to display at the top of the article only (in desktop view only; title coordinates do not display in mobile view), or

  |display=inline,title to display in both places.

• name

  name=X to label the place on maps (default is PAGENAME)

Thus: {{Coord|44.1172|-87.9135|dim:30_region:US-WI_type:event

|display=inline,title|name=accident site}}

Use |display=title (or |display=inline,title) once per article, for the subject of the article, where appropriate.

• Per WP:ORDER, the template is placed at the bottom of the article in the 'end matter', after any navigation templates, but before all categories, including the {{DEFAULTSORT}} template. The {{coord}} template may also be placed within an infobox, instead of at the bottom of the article.
• For full details, refer to {{Coord/doc}}.
• Additional guidance is available at obtaining coordinates and converting coordinates.

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.

Two types of template are available:

• {{coord}} offers users a choice of display format through user styles, emits a Geo microformat, and is recognised (in the title position) by the "nearby" feature of Wikipedia's mobile apps and by external partners such as Google (-Maps and -Earth) and Yahoo.
• Infoboxes such as {{Infobox settlement}}, which automatically emit {{Coord}}.

Depending on the form of the coordinates, the following formats are available.

For just degrees (including decimal values):

{{coord|dd|N/S|dd|E/W}}

For degrees/minutes:

{{coord|dd|mm|N/S|dd|mm|E/W}}

For degrees/minutes/seconds:

{{coord|dd|mm|ss|N/S|dd|mm|ss|E/W}}

where:

• dd, mm, ss are the degrees, minutes and seconds, respectively;
• N/S is either N for northern or S for southern latitudes;
• E/W is either E for eastern or W for western longitudes;
• negative values may be used in lieu of S and W to depict southern and western hemispheres

For example:

The city of Oslo, located at 59° 55′ N, 10° 44′ E, enter:

{{coord|59|55|N|10|44|E}}—which becomes 59°55′N 10°44′E

For a country, like Botswana, less precision is appropriate:

{{coord|22|S|24|E}}—which becomes 22°S 24°E

Higher levels of precision are obtained by using seconds:

{{coord|33|56|24|N|118|24|00|W}}—which becomes 33°56′24″N 118°24′00″W

Coordinates can be entered as decimal values

{{coord|33.94|S|118.40|W}}—which becomes 33.94°S 118.40°W / -33.94; -118.40

Increasing or decreasing the number of decimal places controls the precision. Trailing zeros should be used as needed to ensure that both values have the same level of precision.

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

Generally, the larger the object being mapped, the less precise the coordinates should be. For example, if just giving the location of a city, precision greater than 100 meters is not needed unless specifying a particular point in the city, for example the central administrative building. Specific buildings or other objects of similar size would justify precisions down to 10 meters or even one meter in some cases (1′′ ~15 m to 30 m, 0.0001° ~5.6 m to 10 m).

The final field, following the E/W, is available for specification of attributes, such as type, region and scale.

When adding coordinates, please remove the {{coord missing}} tag from the article, if present.

For more information, see the geographical coordinates WikiProject.

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

See also

• For page naming specifics, see Wikipedia:Naming conventions (numbers and dates).
• Wikipedia:Date formattings
• m:Help:Date formatting feature at Meta
• Displaying numbers and numeric expressions