User:A. di M./MOSNUM

This will be a very brief summary of WP:MOSNUM, intended to eventually replace sections from 10 to 13 of WP:MOS. It should be about 40% of the current size of said sections of WP:MOS, and it won't include recommendations which are seldom useful except to editors of very specialized articles, such as those on scientific notation or non-base-10 numbers.

Figures or words
In general, whole numbers from zero to nine are preferably written in words; greater numbers are preferably written in figures, but may also be written in words if they are expressed in one or two words. However:
 * Be consistent with comparable quantities in the same context: do not write five cats and 32 dogs.
 * Avoid juxtaposing non-comparable quantities both in figures or both in words: write seventy 20-pound banknotes rather than 70 20-pound banknotes.
 * Avoid starting sentences with figures.
 * Days of the month, years, and centuries are normally written in figures.
 * Numbers in mathematical formulas and before unit symbols are written in figures: e.g. 5 min, not five min. On the other hand, both words and figures are acceptable before spelled-out units, as in 5 minutes and five minutes.
 * Figures are usually understood to be more precise than words: in The population of Japan is 128 million people the number is an approximation, only precise to within one million; in The grant is 10,000,000 Swedish kronor, it is exact.
 * Note the difference between Every number except one (there is one exception, which is unspecified) and Every number except 1 (the number 1 is the exception.
 * In names, comply with common usage: e.g. Chanel No. 5 but Fourth Amendment.

Large numbers

 * Digits in numbers greater than or equal to 10,000 are normally grouped with commas every three digits, e.g. 12,345,678. (Templates such as val do this automatically.)  Numbers greater than or equal to 1000 may or may not be grouped 1234 or 1,234; in particular, four-digit serial numbers such as years and page numbers are written without commas.
 * In certain scientific contexts, thin spaces are used instead of commas, but many browser do not render the thin space character correctly: use Template:gaps instead.
 * Avoid giving numbers with false precision or with more precision than needed in the context: for example, The population of Japan is 128 million people, not ... 127,953,234 people. (It is usually unnecessary to explicitly state that such numbers are approximations.)
 * When million and billion occur many times in an article, they may be abbreviated with unspaced "M" and "bn" respectively (£70M, $35bn), after spelling out the word on the first occurrence.
 * In scientific contexts, scientific notation or SI prefixes are preferred.

Decimal fractions

 * 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).
 * 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.
 * The digits after the decimal point can delimited into groups of three (e.g. $0.123$), especially in scientific contexts. Templates such as val do this automatically.

Choice of units

 * In general articles, use the units in the most widespread use in the world for the type of measurement in question. Usually, these are International System of Units (SI) units and non-SI units accepted for use with SI; but there are 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, use the units most appropriate to them (for example, United States customary units in US-related articles).

Conversions

 * When parts of the English-speaking world use a different unit for a type of measurement than the one used in the article, generally provide a parenthetical conversion (e.g. 2375 km); Template:Convert can automatically handle many types of conversion.
 * In some specialized topics it is unnecessary to convert all occurrences of units such as yards in articles about American football, SI units and non-SI units accepted for use with SI in scientific articles, etc.; consider linking the units the first time they are used and/or giving a conversion factor in a footnote or parenthetical note.

Names and symbols

 * Generally use unit names in prose, and unit symbols in tables, mathematical formulas, and parenthetical notes.
 * Unit names are common nouns (even when named after a person) and are not capitalized except where common nouns normally are. For example, 101,325 pascals and 17th century, not 101,325 Pascals or 17th Century.
 * Unit symbols take no final dot or plural ending, are not italicized, and are preceded by numbers in figures, from which they are separated with non-breaking spaces, e.g. 85 kg. The percent sign and the symbols of the degree, prime, and second of arc are unspaced (37%, 45°), but not the symbols of the degree Celsius and the degree Fahrenheit (20 °C).