Numbers

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.

Send feedback about...

Google Developer Documentation Style Guide
Google Developer Documentation Style Guide