View source for User:Tony1/Draft of new-scope MOSNUM

{{MoS guideline|WP:MOSNUM|WP:DATE}} 
{{Style}}
<!-- Please use _quotes_ when mentioning units (as opposed to using units) instead of _italics_ or _bold_ to avoid confusion concerning their proper formatting.-->
This part of the '''[[Wikipedia:Manual of Style|Manual of Style]]''' aims to achieve consistency in the use and formatting of dates and numbers in Wikipedia articles. Consistent standards make articles easier to read, write, and edit. Where this manual provides options, consistency should be maintained within an article, unless there is a good reason to do otherwise. In direct quotations, the original text should be preserved.

In June 2005, the [[Wikipedia:Arbitration Committee|Arbitration Committee]] stated [[Wikipedia:Requests_for_arbitration/Jguk#Optional_styles|that when either of two styles]] is acceptable, it is inappropriate for an editor to change an article from one to the other without substantial reason. For example, with respect to British date formats as opposed to American it would be acceptable to change from American format to British if the article concerned a British subject. [[WP:EDITWAR|Edit warring]] over optional styles (such as 14 February and February 14) is unacceptable. If an article has been stable in a given style, it should not be converted without a style-independent reason. Where in doubt, defer to the style used by the first major contributor.

==Chronological items==
===Year numbering systems===
*'''Uncalibrated (bce) radiocarbon dates:''' Some source materials will indicate whether a date is calibrated or not simply by a change in capitalization; this is often a source of confusion for the unwary reader. Do not give [[Radiocarbon dating#Calibration|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 recognize the distinction between ''bce'' and ''BCE'' / ''BC''.
*Abbreviations indicating long periods of time ago—such as ''[[before present|BP]]'' (before present), as well as various [[annum]]-based units such as ka (kiloannum), Ma (megaannum) and Ga (gigaannum) are given as full words on first occurrence. Where source quotations use the abbreviations [[kya]] (thousand years ago), [[mya (unit)|mya]] (million years ago), or [[bya]] (billion years ago) this should be explained to the reader, as in {{xt|a measured Libby radiocarbon date of 35.1&nbsp;mya [million years ago] had to be calibrated ...}} The kya, mya and bya symbols are deprecated in some fields such as geophysics and geology, but remain common in others, such as anthropology.
**'''BP:''' Do not convert other notations to BP unless you are certain of what you are doing. In some contexts the unit BP is actually defined as "years before January 1, 1950", not "years before the literal present", and the conversion may introduce an error if the date being converted is not a wide approximation ({{xt|18,000&nbsp;BP}}) but a more narrow one or an actual known year. BP years are given as {{xt|18,000&nbsp;BP}} or spelled out as {{xt|18,000 years before present}} (not {{xt|18,000&nbsp;YBP}}, {{xt|18,000 before present}}, {{xt|18,000 years before the present}}, or similar.)

===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 calendar|Julian]] or [[Gregorian calendar]]s is provided, as described below. For example, an article on the early [[history of Islam]] may give dates in both [[Islamic calendar|Islamic]] and Julian calendars. Where a calendar other than the Julian or Gregorian is used, this must be clear to readers.
* Current events are given in the Gregorian calendar.
* Dates before the adoption of the Gregorian calendar on 15&nbsp;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 (calendar)|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 [[Gregorian calendar#Timeline|Continent of Europe from 1582]], the [[British Empire]] from 14&nbsp;September 1752, and Russia from 14&nbsp;February 1918 (see the [[Gregorian calendar]] article).

The dating method used in a Wikipedia article 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 [[WP:FOOT|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, in which the year started on 25 March, [[Annunciation Day]]; see the [[New Year|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 stated. 

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).

==={{anchor|timezones}}Time zones===
{{shortcut|WP:TIMEZONE}}When writing a date, first 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). If it is difficult to judge ''where'', consider what is significant. For example, if a vandal based in Japan attacked a Pentagon computer in the US, use the time zone for the Pentagon, where the attack had its effect. If known, include the [[Coordinated Universal Time|UTC]] date and time of the event in the article, indicating that it is UTC.

==Numbers==
===Delimiting (grouping of digits)===
* Numbers with five or more digits to the left of the decimal point (i.e., 10,000 or more) should be delimited (visually separated into groups so they can be easily parsed) using [[Decimal separator#thousands separator|commas]] every three digits; e.g., {{xt|12,200}} and {{xt|255,200}} and {{xt|8,274,527}} etc.
* Numbers with four digits to the left of the decimal point ''may'' be delimited with a comma; that is, {{xt|there were 1250 head of cattle}} and {{xt|there were 1,250 head of cattle}} are both acceptable.
* Numbers are not delimited when they are part of mailing and shipping addresses, page numbers, and years with four or fewer digits; years with five or more digits use commas (e.g. {{xt|10,400&nbsp;BC}}).
* In scientific articles, particularly those directed to an expert readership, numbers may be delimited with thin spaces using the {{tl|gaps}} template. Coding <code><nowiki>{{gaps|8|274|527}}</nowiki></code> produces {{xt|{{gaps|8|274|527}}}} (note: the thin space character and its [[SGML entity|HTML entity]], <code>&amp;thinsp;</code>, do not render correctly on some browsers or on [[screen reader]]s used by visually impaired people).
* The style of delimiting numbers to the left of the decimal point must be consistent throughout an article.
* Constants in mathematics-oriented articles may be grouped in fives; e.g., {{xt|{{gaps|3.14159|26535|89793|23846|26433|83279|...}}}}.
* 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 {{tl|val}} template, which uses character-positioning techniques rather than distinct characters to form groups. According to [[International Organization for Standardization|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. 

:The recommended progression on Wikipedia is  as follows: {{xt|{{val|1.123}}}}, {{xt|{{val|1.1234}}}}, {{xt|{{val|1.12345}}}}, {{xt|{{val|1.123456}}}}, {{xt|{{val|1.1234567}}}}, {{xt|{{val|1.12345678}}}}, {{xt|{{val|1.123456789}}}}, etc. The <nowiki>{{val}}</nowiki> template handles these grouping details automatically; e.g., <code><nowiki>{{val|1.1234567}}</nowiki></code> generates {{xt|{{val|1.1234567}}}} (with a four-digit group at the end); it can parse no more than a total of 15 significant digits in the [[significand]]. For significands longer than this, editors should delimit high-precision values using the {{tl|gaps}} template; e.g., <code><nowiki>{{gaps|1.234|567|890|123|456}}</nowiki></code> → {{xt|{{gaps|1.234|567|890|123|456}}}}.

===Fractions===
The template {{tl|frac}} is available for representing common fractions. For {{frac|p|q}}, type <nowiki>{{frac|p|q}}</nowiki>. For {{frac|N|p|q}}, type <nowiki>{{frac|N|p|q}}</nowiki>. When copied and pasted, {{frac|N|p|q}} will appear as N+p/q.

===Percentages===
*''Percent'' or ''per cent'' are 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 ({{xt|71%}}, not {{xt|71 %}}).
*In tables and infoboxes, the symbol ''%'' is normally preferred to the spelled-out ''percent'' or ''per cent''. 
*Ranges are preferably formatted with one rather than two percentage signifiers ({{xt|22–28%}}, not {{xt|22%–28%}}). 
*Avoid ambiguity in expressing a change of rates. This can be done by using [[percentage point]]s, not percentages, to express a change in a percentage or the difference between two percentages; for example, {{xt|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 ({{xt|made the commission larger by half.}}). ''Percentage point'' should not be confused with ''[[basis point]]'', which is a hundredth of a percentage point.

===Natural numbers===
(tag removed) mergeto|Manual of Style (mathematics)}}
The [[set]] of [[natural numbers]] has two common meanings: {0, 1, 2, 3, ...}, which may also be called ''non-negative integers'', and {1, 2, 3, ...}, which may also be called ''positive integers''. Use the sense appropriate to the field to which the subject of the article belongs if the field has a preferred convention. If the sense is unclear, and if it is important whether or not zero is included, consider using one of the alternative phrases rather than ''natural numbers'' if the context permits.

===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 {{tl|overline}} can be used. For example, the markup <code><nowiki>14.{{overline|285714}}</nowiki></code> gives ''14.{{overline|285714}}''.

Consider a short explanation of the notation the first time this notation 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 [[base (mathematics)|bases]] other than base ten:
*In computer-related articles, use the [[C (programming language)|C programming language]] prefixes ''0x'' (zero-ex) for hexadecimal and ''0'' (zero) for octal. <!-- Note that 0b is *not* a valid C prefix --> 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: ''137<sub>9</sub>'', ''241<sub>6</sub>'', ''2A9<sub>12</sub>'', ''A87D<sub>16</sub>'' (use <code>&lt;sub></code> and <code>&lt;/sub></code>).
*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&ndash;F for digits from 10 through 15 (''0x5AB3'').

===Scientific notation, engineering notation, and uncertainty===
====Notations====
* The template {{tl|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 formating conventions.
* [[Scientific notation]] is done in the format of one leading digit/decimal marker/rest of digits/×10<sup>''n''</sup>, where ''n'' is the integer that gives one leading digit.
** {{xt|{{val|1.602|e=-19}}}} is a proper use of scientific notation.
** {{xt|{{val|160.2|e=-17}}}} is not a proper use of scientific notation.
* [[Engineering notation]] is done in the format of leading digits/decimal marker/rest of digits/×10<sup>''n''</sup>, where ''n'' is a multiple of 3. The number of leading digits is adjusted accordingly.
** {{xt|{{val|132.23|e=6}}}} is a proper use of engineering notation.
** {{xt|{{val|1.3223|e=8}}}} is a not proper use of engineering notation.
* It is clearer to avoid mixing scientific notation and engineering notation in the same context (e.g., do not write {{xt|A {{val|2.23|e=2|u=m2}} region covered by {{val|234.0|e=6|u=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.

====Uncertainty====
* Uncertainties can be written in various ways:
** Value/±/uncertainty/×/10<sup>n</sup>/unit symbol (e.g., {{val|1.584|0.035|e=23|u=m}})
*** Do not group value and uncertainty in parenthesis before the multiplier (e.g., do not write (15.84&nbsp;±&nbsp;0.35)&nbsp;×&nbsp;10<sup>23</sup>&nbsp;m)
** Value/superscript positive uncertainty/subscript negative uncertainty/×/10<sup>n</sup>/unit symbol (e.g., {{val|15.84|+0.43|-0.23|e=23|u=m}})
** Value(uncertainty in the last digits)/×/10<sup>n</sup>/unit symbol (e.g., {{val|1.584|(35)|e=23|u=m}})
** Value/±/relative uncertainty(percent)/unit symbol (e.g., 15.84&nbsp;±&nbsp;0.25%&nbsp;m)
* The template {{tl|val}} may be used to automatically handle all of this.

== Units of measurement ==
{{Shortcut|WP:UNIT|WP:UNITS|WP:MEASUREMENT}}

The use of units of measurement is guided by the following principles:
* Avoid ambiguity: Aim to write so you cannot be misunderstood.
* Familiarity: The less readers have to look up definitions, the easier it is to be understood. 
* International scope: Wikipedia is not country-specific; apart from some regional or historical topics, use the units in most widespread use worldwide for the type of measurement in question. 

If there is trouble balancing these bullets, consult other editors through the talk page and try to reach consensus.

===Which units to use and how to present them===
Apply the following guidelines when choosing the "primary" unit for a measurement:
*Except in the cases mentioned below, put the units first that are in the most widespread use in the world. Usually, these are [[International System of Units]] (SI) units and [[non-SI units accepted for use with SI]]; but there are [[Metrication#Exceptions|various exceptions]] for some measurements, such as years for long periods of time or the use of feet in describing the altitude of aircraft.
:*With topics strongly associated with places, times or people, put the units most appropriate to them first. For example, in US articles, they usually are [[United States customary units]], and for the UK, they usually are metric units for most measurements, but [[imperial units]] for some measurements such as road distances and draught beer (see, for example, [[Metrication in the United Kingdom]] and the [http://www.timesonline.co.uk/tol/tools_and_services/specials/style_guide/article986731.ece ''Times Online'' style guide] under "Metric").
:* If editors cannot agree on the sequence of units, put the source value first and the converted value second. If the choice of units is arbitrary, use SI units as the main unit, with converted units in parentheses.
:* Avoid inconsistent usage. Write {{xt|a 600 metre (2000 ft) hill with a 650 metre (2,100 ft) hill}}, not {{xt|a 2,000 foot (610 m) hill with a 650 metre (2,100 ft) hill.}} 
:* Nominal and defined values should be given in the original units first, even if this makes the article inconsistent: for example, {{xt|When the Republic of Ireland adopted the metric system, the road speed limit in built-up areas was changed from {{convert|30|mph|km/h|0}} to {{convert|50|km/h|mph|0}}.}} (The focus is on the change of units, not on the 3.6% increase.)
:* Avoid ambiguous unit names (e.g., write {{xt|[[imperial gallon|imperial&nbsp;gallon]]}} or {{xt|[[US gallon|US&nbsp;gallon]]}} rather than {{xt|[[gallon]]}}). Only in the rarest of instances should ambiguous units be used, such as in direct quotations, to preserve the accuracy of the quotation.
* In scientific articles, use the units employed in the current [[scientific literature]] on that topic. This will usually be [[International System of Units|SI]], but not always; for example, [[natural units]] are often used in relativistic and quantum physics, and [[Hubble's constant]] should be quoted in its most common unit of {{xt|(km/s)/Mpc}} rather than its SI unit of {{xt|s<sup>−1</sup>}}.
* Some disciplines use units not approved by the BIPM, or write them differently from BIPM-prescribed format. When a ''clear majority'' of the sources relevant to those disciplines use such units, articles should follow this (e.g., using {{xt|[[Cubic centimetre|cc]]}} in automotive articles and not {{xt|cm<sup>3</sup>}}). Such non-standard units are always linked on first use.
* Use familiar units rather than obscure units—do not write over the heads of the readership (e.g., a general-interest topic such as black holes would be best served by having mass expressed in solar masses, but it might be appropriate to use Planck units in an article on the mathematics of black hole evaporation).

===Unit conversions===
{{shortcut|MOS:CONVERSIONS}}
* Generally, conversions to and from metric units and [[United States customary units|US]] or [[Imperial units|imperial]] units should be provided, except:
** When inserting a conversion would make a common expression awkward ({{xt|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 values should use a level of precision similar to that of the source value, so {{xt|the Moon is 380,000 kilometres (240,000&nbsp;mi) from Earth}}, not {{xt|(236,121&nbsp;mi)}}. However, small numbers may need to be converted to a greater level of precision where rounding would cause a significant distortion, so {{xt|one mile (1.6&nbsp;km)}}, not {{xt|one mile (2&nbsp;km)}}.
* [[:Category:Conversion templates]] can be used to convert and format many common units, including {{tl|convert}}, which includes non-breaking spaces.
* In a direct quotation, always keep the source units.
** Conversions required for units cited within direct quotations should appear within square brackets in the quote.
** Alternatively, you can annotate an obscure use of units (e.g. {{xt|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 [[WP:CITE#HOW|the style guide for citation]], [[Wikipedia:Footnotes|footnoting]] and [[Wikipedia:Citing sources|citing sources]].
* Measurements should be accompanied by a proper citation of the source using a method described at [[WP:CITE#HOW|the style guide for citation]].
* Where [[Wikipedia:Footnotes|footnoting]] or [[Wikipedia:Citing sources|citing sources]] for values and units, identify both the source and the original units.

===Avoiding ambiguities===
* Identify and define ambiguous units on their first use in an article. 
** Avoid using unit abbreviations that have conflicting meanings in common units systems such as [[International System of Units|SI]] and [[United States customary units|US customary units]]:
*** Use {{xt|nmi}} (or {{xt|NM}}) to abbreviate ''[[nautical mile]]'' rather than {{xt|nm}} (''nanometre'').
*** Use {{xt|kn}} to abbreviate ''[[knot (speed)|knot]]'': {{xt|kt}} could be confused with kilotonne; {{xt|kN}} could be confused with kilonewton.
*** Link such units to their definitions on first use.
** Some different units share the same name. These examples show the need to be specific.
*** Use {{xt|[[nautical mile]]}} or {{xt|[[mile#Statute miles|statute mile]]}} rather than {{xt|mile}} in nautical and aeronautical contexts.
*** Use {{xt|[[long ton]]}} or {{xt|[[short ton]]}} and not just {{xt|ton}}; these units have no symbol or abbreviation and are always spelled out. The ''[[tonne]]'', 1000 kilograms, is officially known as the ''metric ton'' in the US. Whichever name is used, the symbol is {{xt|t}}. 
*** Use {{xt|[[troy weight|troy]]}} or {{xt|[[avoirdupois]] [[ounce]]}} and not just {{xt|ounce}} in articles about precious metals, black powder, and gemstones.
*** Use {{xt|[[fluid ounce]]}} explicitly to avoid confusion with weight, and specify, if it is Imperial, US or other fluid ounce.
*** Use {{xt|[[US gallon|US&nbsp;gallon]]}} or {{xt|[[imperial gallon]]}} rather than just {{xt|gallon}} (also with quarts, pints, and fluid ounces).
*** A ''[[calorie]]'' (symbol {{xt|cal}}) refers to a ''[[gram calorie]]'' while the ''[[kilocalorie]]'' (symbol {{xt|kcal}}) refers to the ''[[kilogram calorie]]'' (also known as ''[[small calorie]]'' and ''[[large calorie]]'' respectively). When used in a nutrition related article, use the kilocalorie as the primary unit. In US-related articles, use the synonym {{xt|dietary calorie}} with a one-time link to ''[[kilogram calorie]]''.
** For bits and bytes, specify whether the [[binary prefix|binary]] or [[SI prefix|decimal]] meaning of the prefixes [[kilo]] ({{xt|k}}, {{xt|K}}), [[mega]] ({{xt|M}}), [[giga]] ({{xt|G}}) and [[tera]] ({{xt|T}}) is intended. See [[#Quantities of bytes and bits|Quantities of bytes and bits]].
* In tables and infoboxes, use unit symbols and abbreviations—do not spell them out.
* It may be appropriate to note that given quantities and conversions are approximate.
** When part of a full sentence, write ''approximately'' in full (e.g., write {{xt|Earth's radius is approximately 6,400 kilometres}}, not {{xt|Earth's radius is approx. 6,400 kilometres}} or {{xt|Earth's radius is ~ 6,400 kilometres}}). 
** In tables, infoboxes, or within brackets, use a tilde (''~'') or use ''approx.'' (e.g, write {{xt|The [[Tonnage|capacity of a ship]] is sometimes expressed in [[gross register ton]]s, a unit of volume defined as 100 cubic feet (~2.83 m<sup>3</sup>)}}).
** Do not note a conversion as approximate where the initial quantity has already been noted as such, (e.g., write {{xt|Earth's radius is approximately 6,400&nbsp;km (4,000&nbsp;mi)}}, not {{xt|Earth's radius is approximately 6,400&nbsp;km (approx. 4,000&nbsp;mi)}}.

===Unit names and symbols===

====Conventions====
* Where space is limited, such as in tables, infoboxes, and parenthetical notes, and in mathematical formulas, unit symbols are preferable. In prose it is usually better to spell out unit names, but symbols may also be used when a unit (especially one with a very long name) is used many times in an article. However, spell out the first instance of each unit in an article: for example {{xt|The typical batch is 250 kilograms&nbsp;... and then 15&nbsp;kg of emulsifier is added.}}
* If a unit symbol which can be unfamiliar to a general audience is used in an article, it should be shown parenthetically after the first use of the full unit name: for example, {{xt|His initial betatron reached energies of 2.3 [[megaelectronvolt]]s (MeV), while subsequent betatrons achieved 300&nbsp;MeV.}}
* Numerical ranges use unspaced en dashes if only one unit symbol is used at the end (e.g., {{xt|5.9–6.3&nbsp;kg}}), and spaced en dashes if two symbols are used (e.g., {{xt|3000&nbsp;nm – 1&nbsp;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., {{xt|from 5.9 to 6.3 kilograms}}, {{xt|from 5.9 kilograms to 6.3 kilograms}}, {{xt|from 5.9 to 6.3&nbsp;kg}} and {{xt|from 5.9&nbsp;kg to 6.3&nbsp;kg}} are all acceptable).
* When dimensions are given, each number should be followed by a unit name or symbol (e.g., write {{xt|1&nbsp;m × 3&nbsp;m × 6&nbsp;m}}, not {{xt|1 × 3 × 6&nbsp;m}} or {{xt|1 × 3 × 6&nbsp;m<sup>3</sup>}}).
=====Unit names=====
* Unit names, even those named after people, are common nouns. They are not capitalized when written in full, except where common nouns take a capital. Write {{xt|The pascal is a unit of pressure}}, ''not'' {{xt|The Pascal is a unit of pressure}}. In ''degree Celsius'' and ''degree Fahrenheit'', the ''d'' is not usually capitalized, but the ''C'' and the ''F'' are. (The common noun is ''degree'', ''Celsius'' being a proper adjective.)
* When unit names are combined by multiplication, separate them with a [[hyphen]] or space (e.g., {{xt|newton-metre}} or {{xt|newton metre}}). The plural is formed by pluralizing the last unit name (e.g., {{xt|ten newton-metres}}). 
* When unit names are combined by division, separate them with ''per'' (e.g., {{xt|meter per second}}, not {{xt|meter/second}}). The plural is formed by pluralizing the unit preceding the ''per'', since it reads ''this many units of this'' per ''one unit of this'' (e.g., {{xt|ten metres per second}}).
* When they form a compound adjective, values and unit names [[WP:HYPHEN|should be separated by a hyphen]]: for example, {{xt|a five-day holiday}}.

=====Unit symbols=====
* Units symbols are preceded by figures, not by spelled-out numbers: for example, {{xt|5&nbsp;min}}, not {{xt|five&nbsp;min}}.
* Values and unit symbols are always separated by a [[non-breaking space]]. The {{tl|nowrap}} template or the <code><nowiki>&amp;nbsp;</nowiki><code> character can be used for this purpose. For example, use {{xt|10&nbsp;m}} or {{xt|29&nbsp;kg}}, not {{xt|10m}} or {{xt|29kg}}.
** Exceptions: Non-alphabetic symbols for degrees, minutes and seconds ''for angles and coordinates'' and the percent sign are unspaced (for example, {{xt|5°&nbsp;24′&nbsp;21.12″&nbsp;N}} for coordinates, {{xt|90°}} for an angle, {{xt|47%}} for a percentage, but {{xt|18&nbsp;°C}} for a temperature). See also ''[[Wikipedia:Manual of Style (dates and numbers)#Geographical coordinates|Manual of Style—Geographical Coordinates]]''.
* Write unit symbols in upright roman type. (Italic type is normally reserved for variables and the like.) (e.g., {{xt|10&nbsp;m}} or {{xt|29&nbsp;kg}}, not {{xt|10&nbsp;''m''}} or {{xt|29&nbsp;''kg''}}).
* Standard symbols for units are undotted; e.g., {{xt|m}} for the metre (not {{xt|m.}}), {{xt|kg}} for the kilogram (not {{xt|kg.}}), {{xt|in}} for the inch (not {{xt|in.}}, the quotation mark&nbsp;{{xt|"}}, or the double prime&nbsp;{{xt|&Prime;}}), and {{xt|ft}} for foot (not {{xt|ft.}}, the apostrophe&nbsp;{{xt|'}}, or the prime&nbsp;{{xt|&prime;}}).
** Non-standard abbreviations should be dotted.
* Symbols have no plural form—an ''s'' is never appended (e.g., {{xt|kg}}, {{xt|km}}, {{xt|in}}, {{xt|lb}}, not {{xt|kgs}}, {{xt|kms}}, {{xt|ins}}, {{xt|lbs}}. Write {{xt|bit}}, not {{xt|bits}} unless ''bits'' is used as a word rather than a symbol).
* When unit symbols are combined by multiplication, use a [[middle dot]] (<code>&amp;middot;</code>) or a [[non-breaking space]] (<code>&amp;nbsp;</code>) to separate the symbols. For example, {{xt|ms}} is the symbol for the millisecond, while {{xt|m&middot;s}} or {{xt|m&nbsp;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 {{xt|m/s}}, not {{xt|mps}}) or use negative exponents ({{xt|m·s<sup>&minus;1</sup>}}). Exceptions include '''mph''' for the [[mile per hour]], '''psi''' for [[pounds per square inch]], etc.
** There should be no more than one slash per compound unit symbol (e.g., {{xt|kg/(m·s)}}, not {{xt|kg/m/s}} or {{xt|kg/m·s}}).
* Powers of unit symbols are expressed with a superscript exponent (write {{xt|5&nbsp;km<sup>2</sup>}}, not {{xt|5&nbsp;km^2}}).
** A superscript exponent indicates that the unit is raised to a power, not the unit ''and'' the quantity (3 [[metres]] squared is 9 [[square metre]]s, or 9&nbsp;m<sup>2</sup>).
** For areas and volumes, squared and cubed US customary or imperial length units may instead be rendered with '''sq''' and '''cu''' between the number and the unit symbol (e.g., {{xt|15&nbsp;sq&nbsp;mi}} and {{xt|3&nbsp;cu&nbsp;ft}}, not {{xt|15&nbsp;mi&nbsp;sq}} and {{xt|3&nbsp;ft&nbsp;cu}}).
** The symbols '''sq''' and '''cu''' are not used with BIPM-approved unit symbols.
** Avoid  the Unicode characters '''²''' and '''³'''. They are harder to read on small displays, and are not aligned with superscript characters (e.g., ''x<sup>1</sup>x²x³x<sup>4</sup>'' vs. ''x<sup>1</sup>x<sup>2</sup>x<sup>3</sup>x<sup>4</sup>''). Instead, use superscript markup, created with <nowiki><sup></sup></nowiki>.

====Units and symbols often written incorrectly====

* The [[degree symbol]] is '''°''' (<code>&amp;deg;</code>);. Using any other symbol (e.g., [[masculine ordinal]] '''º''' or [[ring (diacritic)|ring]] above '''˚''') for this purpose is incorrect.
* The symbol for the [[bit]] is '''bit''', not '''b'''. The [[byte]] may be represented by either one of the symbols '''B''' and '''byte''', but not '''b''' or '''o''' ({{langx|fr|octet}}).  Unless explicitly stated otherwise, one byte is eight bits (see [[Byte#History|History of ''byte'']]).
** By extension, the symbols for the units of data rate [[kilobit per second]], [[megabit per second]] and so on are '''kbit/s''' (not '''kbps''' or '''Kbps'''), '''Mbit/s''' (not '''Mbps''' or '''mbps'''), etc. Similarly, [[kilobyte per second]] and [[megabyte per second]] are '''kB/s''' (not '''kBps''' or '''KBps''') and '''MB/s''' (not '''Mbps''' or '''MBps''').
* The symbols for the [[degree Celsius]], the [[degree Fahrenheit]] and the [[kelvin]] are '''°C''' (not '''C'''), '''°F''' (not '''F'''), and '''K''' (not '''°K'''). ('''C''' and '''F''' are the symbols for the [[coulomb]] and the [[farad]]; '''°K''' is the symbol for the degree Kelvin, the pre-1968 name of the kelvin.)
* For reasons of legibility, the preferred symbol for the unprefixed [[liter]] is upper-case '''L'''.
* If you need to express [[years]] as a unit, use the symbol '''a''' ({{langx|la|annum}}) along with SI prefixes (e.g., write {{xt|The half life of thorium-230 is 77&nbsp;ka}} and {{xt|The Cambrian is a geologic period that dates from 540&nbsp;Ma to 490&nbsp;Ma}}).
** There are many types of years (see [[year]]). When years are not used in the layman's meaning (e.g., {{xt|Julie is 20 years old}}) clarify which type of year is meant.
* Roman prefixes are not used ('''M''' for 10<sup>3</sup>, '''MM''' for 10<sup>6</sup>, '''B''' for 10<sup>9</sup>). Use SI prefixes instead.

====Quantities of bytes and bits {{anchor|Binary prefixes}}====
{{shortcut|WP:COMPUNITS}}

In quantities of [[bit (computing)|bit]]s and [[byte]]s, the prefixes ''kilo'' (abbreviated ''k'' or ''K''), ''mega'' (''M''), ''giga'' (''G''), etc. are ambiguous. They may be based on a decimal system (like the standard [[International System of Units|SI]] prefixes), meaning 10<sup>3</sup>, 10<sup>6</sup>, 10<sup>9</sup>, etc., or they may be based on a binary system, meaning 1024 (2<sup>10</sup>), 1024<sup>2</sup>, 1024<sup>3</sup>, 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 and disk storage.
{{Quantities of bytes}}
The following recommendations are made for the use of these prefixes in Wikipedia articles:
* Editors should specify if the binary or decimal meanings of ''K'', ''M'', ''G'', etc. are intended as the primary meaning. 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]], and a binary definition for Windows file sizes, despite files usually being stored on hard drives).
** Where consistency is not possible, specify wherever there is a deviation from the primary definition.
* Disambiguation should be shown in bytes or bits, with clear indication of whether in binary or decimal base. There is no preference in the way to indicate the number of bytes and bits, but the notation style should be consistent within an article. Acceptable examples include:
::{{xt|A 64&nbsp;MB ({{nowrap|64 × 1024<sup>2</sup> bytes)}} video card and a 100&nbsp;GB ({{nowrap|100 × 1000<sup>3</sup> bytes)}} hard drive}}
::{{xt|A 64&nbsp;MB ({{nowrap|64 × 2<sup>20</sup> bytes)}} video card and a 100&nbsp;GB {{nowrap|({{val|100|e=9|u=bytes}})}} hard drive}}
::{{xt|A 64&nbsp;MB (67,108,864&nbsp;bytes) video card and a 100&nbsp;GB (100,000,000,000&nbsp;bytes) hard drive}}
:Avoid inconsistent combinations such as {{xt|A 64&nbsp;MB (67,108,864&nbsp;bytes) video card and a 100&nbsp;GB {{nowrap|(100 × 1000<sup>3</sup> bytes)}} hard drive}}. Footnotes, such as those seen in [http://en.wikipedia.org/w/index.php?title=Power_Macintosh_5500&oldid=218088888 {{nowrap|Power Macintosh 5500}}], may be used for disambiguation.

The [[Binary prefixes#IEC standard prefixes|IEC standard prefixes]] ''kibi-'', ''mebi-'', ''gibi-'', etc. (symbols ''Ki'', ''Mi'', ''Gi'', etc.) are [[Wikipedia talk:Manual of Style (dates and numbers)/Archive/Complete rewrite of Units of Measurements (June 2008)|not familiar]] to most Wikipedia readers, 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.

===Adopting suggestions from standards bodies===
Wikipedia's style guides do not necessarily conform to the prescriptions of [[standards organization|standards bodies]] (e.g., [[International Bureau of Weights and Measures|BIPM]] and their [[International System of Units|SI]], the [[International Electrotechnical Commission|IEC]], and the [[International Organization for Standardization|ISO]]).

For instance, SI guidelines regarding the [[percent]] symbol (%) are often disregarded in practice. According to the BIPM's [http://www.bipm.org/en/si/si_brochure/chapter5/5-3-2.html#5-3-3 SI brochure (subsection 5.3.3)], a space is always used to separate the unit symbol from the numeric value. Notable exceptions are the unit symbols for degree, minute, and second of [[plane angle]] (°, ′, and ″). However, according to the BIPM's [http://www.bipm.org/en/si/si_brochure/chapter5/5-3-7.html SI brochure (subsection 5.3.7)], the exception does not apply to the percent symbol, stating: ''"When [the percent symbol] is used, a space separates the number and the symbol %."'' This practice has not been well adopted with regard to the % symbol, and per current Wikipedia consensus, is contrary to [[Wikipedia:Manual_of_Style#Percentages|Wikipedia's ''Manual of Style'']]. Use {{xt|50%}}, not {{xt|50&nbsp;%}}.

Wikipedia follows common practice regarding [[byte]]s and other data traditionally quantified using [[binary prefix]]es (e.g., mega- and kilo-, meaning 2<sup>20</sup> and 2<sup>10</sup> respectively) and their unit symbols (e.g., MB and KB). Despite the IEC's 1998 guideline creating several new binary prefixes (e.g., mebi-, kibi-) to distinguish the meaning of the decimal [[SI prefix]]es (e.g., mega- and kilo-, meaning 10<sup>6</sup> and 10<sup>3</sup> respectively) from the binary ones, consensus on Wikipedia currently favours the retention of the binary prefixes in computing-related contexts. Use {{xt|256&nbsp;MB of RAM}}, not {{xt|256&nbsp;MiB of RAM}}.

==Currencies==
{{shortcut|WP:$|WP:£|WP:€|MOS:CURRENCY}}
{{see also|Wikipedia:WikiProject Numismatics/Style#Article titles}}

==Common mathematical symbols==
: ''See also: [[Wikipedia:Manual of Style (mathematics)|Manual of Style (mathematics)]].''
* For a negative sign or subtraction operator, use a minus sign (''−''). You can input a minus sign by either keying in ''<nowiki>&amp;minus;</nowiki>'' or by clicking on it in the insert box beneath the edit window (located between the ''±'' and ''×'' signs). Do not use an [[Wikipedia:Manual_of_Style#En_dashes|en dash]] (''&ndash;''), do not use a [[Wikipedia:Manual_of_Style#Hyphens|hyphen]] (''-'') unless writing code, and do not use an [[Wikipedia:Manual_of_Style#Em_dashes|em dash]] (''&mdash;'').
*For a multiplication sign, use ''×'', which can be input by clicking on it in the edit toolbox under the edit window or by keying in ''<nowiki>&amp;times;</nowiki>'' (however, the letter ''x'' is accepted as a substitute for ''by'' in such terms as ''4x4'').
<center>
{|class="wikitable" style="align: center; text-align: center;"

|+Common mathematical symbols
|-
! Name
! Operation
! Other use
! Symbol
! Wikicode
! [[ASCII]]
! [[Unicode]]
! As [[binary operator]] <br /> (e.g., 1&nbsp;+&nbsp;1)
! As [[unary operator]] <br /> (e.g., +1)
|-
| [[Plus sign]]
| [[Addition]]
| Positive sign
| +
| &amp;plus;
| &amp;#43;
| U+002B
| Spaced
| Unspaced 
|-
|Plus or minus
| Addition or subtraction
| Positive or negative sign
| ±
| &amp;plusmn;
| &amp;#177;
| U+00B1
| Spaced
| Unspaced
|-
| Minus or plus
| Subtraction or addition
| Negative or positive sign
| ∓
| —
| &amp;#8723;
| U+2213
| Spaced
| Unspaced
|-
| [[Minus sign]]
| [[Subtraction]]
| Negative sign
| −
| &amp;minus;
| &amp;#8722;
| U+2212
| Spaced
| Unspaced
|-
| [[Multiplication sign]], cross
| [[Multiplication]], [[vector product]]
| —
| ×
| &amp;times;
| &amp;#215;
| U+00D7
| Spaced
| —
|-
| [[Division sign]], obelus
| [[Division (mathematics)|Division]]
| —
| ÷
| &amp;divide;
| &amp;#247;
| U+00F7
| Spaced
| —
|-
| [[Equal sign]]
| [[Equality|Equation]]
| —
| =
| —
| &amp;#61;
| U+003D
| Spaced
| —
|-
| [[Not equal sign]]
| Non-equation
| —
| ≠
| &amp;ne;
| &amp;#8800;
| U+2260
| Spaced
| —
|-
| [[Approximate sign]]
| [[Approximation]]
| —
| ≈
| &amp;asymp;
| &amp;#8776;
| U+2248
| Spaced
| —
|-
| [[Less than sign]]
| [[Inequality|Inequation]]
| —
| <
| &amp;lt;
| &amp;#60;
| U+3C
| Spaced
| —
|-
| [[Less than or equal to]]
| Inequation 
| —
| ≤
| &amp;le;
| &amp;#8804;
| U+2264
| Spaced
| —
|-
| [[Greater than sign]]
| Inequation
| —
| >
| &amp;gt;
| &amp;#62;
| U+3E
| Spaced
| —
|-
| [[Greater than or equal to]]
| Inequation 
| —
| ≥
| &amp;ge;
| &amp;#8805;
| U+2265
| Spaced
| —
|}
</center>

==Unnecessary vagueness==

Use accurate measurements whenever possible.
<center>
{| class="wikitable"
|- valign="top"
! Vague || Precise           
|- valign="top"
|The wallaby is small || The average male wallaby is 1.6&nbsp;metres (63&nbsp;in) from head to tail. 
|- valign=top
|''Prochlorococcus marinus'' is a tiny cyanobacterium. || The cyanobacterium ''Prochlorococcus marinus'' is 0.5 to 0.8&nbsp;micrometre across. 
|- valign=top
|The large oil spill stretched a long way down the Alaskan coast. || The oil spill that drifted down the Alaskan coast was 3 statute miles (5&nbsp;km) long and 1,000&nbsp;feet (300&nbsp;m) wide.
|-
| A beautiful little house in Malibu || A $400,000 residential property in Malibu
|}
</center>

==Geographical coordinates==

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

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

:'''Quick guide''':

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

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

Two types of template are available:
* {{tl|coord}}, which has replaced the ''coor'' family (and combined their functionality), offers users a choice of display format through [[Help:User style|user style]]s, emits a [[Geo microformat]], and is supported by Google Earth.
*Infoboxes such as {{tl|Infobox settlement}}

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

For just degrees (including decimal values):
: <code>&#123;{coord|''dd''|''N/S''|''dd''|''E/W''}&#125;</code>
For degrees/minutes:
: <code>&#123;{coord|''dd''|''mm''|''N/S''|''dd''|''mm''|''E/W''}&#125;</code>
For degrees/minutes/seconds:
: <code>&#123;{coord|''dd''|''mm''|''ss''|''N/S''|''dd''|''mm''|''ss''|''E/W''}&#125;</code>

where:
* ''DD'', ''MM'', ''SS'' are the degrees, minutes, seconds, listed in sequence
* ''N/S'' is either ''N'' or ''S'', depending on which hemisphere, and
* ''E/W'' is either ''E'' or ''W'', depending on which hemisphere
* negative values may be used in lieu of ''S'' and ''W''

For example:

The city of [[Oslo]], located at '''59° 55&prime; N, 10° 44&prime; E''', enter:
:<code><nowiki>{{coord|59|55|N|10|44|E}}</nowiki></code> &mdash; which becomes {{coord|59|55|N|10|44|E}}

A country, like [[Botswana]], less precision is appropriate:
:<code><nowiki>{{coord|22|S|24|E}}</nowiki></code> &mdash; which becomes {{coord|22|S|24|E}}

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

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

Increasing or decreasing the number of decimal places can control the precision. Trailing zeroes should be included. 

[[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 you have added the coordinates, you might want to remove the {{tl|coord missing}} tag from the article, if present. 

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

Templates other than {{tl|coord}} should use the following variables 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)]].
* [[m:Help:Date formatting feature]] at Meta
* [[m:Help:Calculation#Displaying numbers and numeric expressions|Displaying numbers and numeric expressions]]

== Notes ==
{{reflist}}