## Ordinal numbers

Spell out all ordinal numbers in text.

#### Examples

Not recommended: 1st, 5th, 12th, 43rd

Recommended: first, fifth, twelfth, forty-third

## Numbers as words

In general, spell out the following:

- Numbers from zero through nine.
A number that starts a sentence.

Recommended: Fifteen directories are created.

In some cases it's better to rearrange the sentence so that the number appears later.

Not recommended: 164MB is generally considered too large a file to send as an attachment.

Recommended: In general, avoid sending files larger than 164MB as attachments.

**Exception:**It's okay, but non-optimal, to begin a sentence with a four-digit year.A number that is followed by a numeral.

Recommended: This procedure creates fifteen 100,000-byte files.

*But*Recommended: This procedure creates 15 of the 100,000-byte files.

## Numbers as numerals

In general, use numerals for the following:

Numbers 10 and greater.

**Exceptions:**Always use numerals for the following items, even if they're less than 10:- Version numbers.
- Technical quantities, such as amounts of memory, amounts of disk space, numbers of queries, or usage limits.
- Page numbers.
- Chapter numbers, sections, pages, and so on.
- Prices.
- Numbers without units, such as numbers used in mathematical expressions.

Numbers less than 10 when they appear in the same sentence with numbers greater than 9.

Recommended: The menu contains 15 options but 6 of them are disabled.

- Negative numbers.
- Most fractions.
- Percentages.
- Decimals.
For decimal numbers less than one, place a zero in front of the decimal point.

Recommended: 0.3 inch

- Measurements.
- Numbers in a range.

## Fractions

- Express fractions as decimal numbers, when possible.
When expressing fractions as words, connect the numerator and denominator with a hyphen unless one of them is already hyphenated.

Recommended: two-fifths

Recommended: five sixty-fourths

## Percentages

In general, use numerals and the percent sign (%), without a space between them.

**Exception:** If the percentage starts the sentence, then spell out both
the number and the word *percent*.

Recommended: Forty percent of the files

## Ranges of numbers

Use numerals for ranges.

In theory, the correct punctuation for a range of numbers is an en dash. But in practice, for simplicity we use a hyphen with no space either side of it.

Recommended: 2012-2016

See also the Hyphens page.

## More examples

Recommended:

- two-day total
- version 3
- four options
- five minutes
- 6 queries/second
- 8 pixels
- nine developers
- 10 chapters
- 18 years old
- 27 minutes
- 50MB/s
- 64-bit
- 102 degrees
- 728 shipments
- 18,000,000 users
- 40%

## Commas and decimal points in numbers

Use commas and decimal points in accordance with standard American number-formatting.

Specifically: in numbers four or more digits long, use commas to set off groups of three digits, counting leftward from the decimal point, in the standard American style.

Use a period for a decimal point, also in the standard American style.

#### Examples of comma grouping

Not recommended: The limit is 1532784 bytes per day.

Recommended: The limit is 1,532,784 bytes per day.

Not recommended: The API supports up to 2000 vertices.

Recommended: The API supports up to 2,000 vertices.

For more about decimal points and digit group separators, see Wikipedia's decimal mark entry.