Ordinal numbers

Spell out all ordinal numbers in text.


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.


    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.


  • 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


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


  • 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.

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Google Developer Documentation Style Guide
Google Developer Documentation Style Guide