Numbers Edit

Highlight: Spell out whole numbers from zero through nine. Follow proper formatting for numbers.

Numbers as words

  • Spell out whole numbers from zero through nine, with exceptions as described in Numbers as numerals.

    • three databases
    • zero percent
    • 17 documents
    • 15,493 entries
  • Use the spelled-out number when it starts a sentence.
    Recommended: Twenty files were copied.

    You can rewrite the sentence so that the number doesn’t start the sentence.
    Not recommended: 1500 records were cleared from the old directories.

    Recommended: Freeing up some space in the old directories, almost 1500 records were cleared.
  • When a number is followed by another numeral, use a numeral for one and spell out the other.
    Recommended: The folder contains three 256-bit AES encrypted files.

    Recommended: The folder contains 3 of the 256-bit AES encrypted files.
  • If one item requires a numeral, use numerals for all the other items of that type.
    Recommended: One instance of the application runs on 2 cores, one on 4 cores, and the third one on 6 cores.
  • Spell out indefinite, casual, ambiguous, and rounded numbers.
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  • Spell out zero through nine and use numerals for 10 or greater for days, weeks, and other units of time.

    • 24 hours
    • 15 days
    • four years

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Numbers as numerals

  • Use numerals for numbers 10 and greater.
    Recommended: There are a total of 70 users currently online.

    Exceptions: Use numerals for the following instances in all cases, even when they’re less than 10:

    • Page numbers.
    • Chapter, section, volumes, part, and step numbers.
    • Rows and columns in tables and lists.
    • Technical quantities such as memory, disk space, lines of code, etc.
    • Version numbers.
    • Prices of goods and services.
    • Numbers without units.
  • Use numerals for measurements of distance, size, weight, temperature, pixels, length, and so on—even if the number is less than 10.

    • 50 px
    • 7 miles
    • 2 feet, 2 inches
    • 39 lb
    • 55 square meters
  • Use numerals for describing dimensions.
  • When numerals less than 10 appear in the same sentence along with numbers greater than 9, use numerals.
    Recommended: Of the 22 users online, 8 have registered accounts.
  • Use numerals while referring to decimals. For decimals less than 1, put a zero before the decimal point.
    Recommended: 0.54 square miles
  • Use numerals while referring to negative numbers.
    Recommended: The error occurred due to the count being changed to -2.
  • If you direct the user or reader to enter a number, use numerals.
    Recommended: Enter 3 as the value.
  • When you write numbers in a range, use numerals.
  • While indicating the time of day, use numerals.
  • Use numerals for percentages.
  • Use numerals for fractions.

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Ordinal numbers

Write all ordinal numbers as fully-spelled words.


Not recommended: 1st, 2nd, 3rd, 7th, 18th, 99th

Recommended: First, second, third, seventh, eighteenth, ninety-ninth

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Numbers as Roman numerals

Avoid using Roman numerals. Instead use standard Arabic numerals in your documentation.

You can use Roman numerals to denote steps or sub-steps in procedures.

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Commas and decimal points in numbers

Use commas and decimal points as per American number formatting. Use commas in numbers having four or more digits, setting off groups of three digits left of the decimal point. Don’t use spaces, commas, or any separators to the right of the decimal point.

Use a period to denote a decimal point.


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Recommended: You can carry out a maximum of 1,500,000 transactions per month.

Not recommended: The total cost may exceed $17000.

Not recommended: The total cost may exceed $17 000.

Recommended: The total cost may exceed $17,000.

Not recommended: Your account will be credited 0.079 635 credits every two hours.

Recommended: Your account will be credited 0.079635 credits every two hours.

For decimals less than 1, put a zero before the decimal point.


Recommended: 0.54 square miles

When expressing measurements where the unit of measurement is spelled out, use the plural form when the quantity is a decimal fraction. Use the singular form of the unit only when the quantity is 1.


  • 0 inches
  • 0.77 inches
  • 1 inch
  • 70 inches

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Express fractions as decimal numbers whenever possible, but expressing them as words or symbols as is acceptable. Don’t use slashes with fractions, as they may be difficult to comprehend. Using slashes with fractions could be misunderstood as alternatives or combinations. When expressing fractions as words, use a hyphen to link the numerator with the denominator, unless one of them is already hyphenated.


Not recommended: 3/4

Recommended: ¾

Recommended: 0.75

Recommended: 75%

Recommended: three-fourths

Not recommended: 4 1/2


Recommended: 4.5

Recommended: four one-halves

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Denote percentages with the numeral and a percent sign (%) after it, without a space between them.
Exception: If the percentage starts the sentence, then spell out both the number and the word percent.


Recommended: 99 percent completed.

Recommended: The progress bar is at 99%.

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Mention to the reader distinctly what country’s currency that you’re referring to. For example, the dollar sign ($) can be mistaken for US dollars, Canadian dollars, Australian dollars, and multiple other currencies. Use ISO defined country or region codes to depict international currencies, if possible.

When you’re referencing specific amounts of money, use the currency code, followed by the amount, with no space.


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Capitalize the country or region, but lowercase the name of currencies.


  • US dollar
  • Indian rupee
  • Japanese yen

For US dollars, use the dollar sign at the beginning ($) of the currency. Use a comma to delineate the thousands place of whole currency; that is, use a comma in amounts that have four or more digits. Use a period to delineate whole currency and fractions of currency. Don’t use any punctuation or spaces to the right of the decimal.


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Recommended: You have $15.39512 in usable credits.

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Not recommended: The total cost may exceed $17000.

Not recommended: The total cost may exceed $17 000.

Recommended: The total cost may exceed $17,000.

If it’s clear which currency you’re referring to, it’s acceptable to only use the symbol rather than the word or country code itself.

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Use numerals for dimensions.

Use a lowercase x between the numerals in the dimensions, with no space between the numerals and the x. You can also use the multiplication sign (×). Use a space before and after the multiplication sign.


Not recommended: 144 x 144 px

Recommended: 144×144 pixels

Recommended: 50-foot fiber optic cable

Recommended: 3840×2160

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Write exponents using standard mathematical notation bn, where the base is b and the exponent or power is n.


Recommended: 34

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Ranges of numbers

En dashes are generally used to indicate a range of numbers, the minus sign, or negative numbers. Although you can use en dashes for these purposes, you can also use hyphens or the word to for numerical ranges.

Use an en dash indicate a range of numbers such as values or dates. Don’t add spaces before and after the en dash or the hyphen.


Not recommended: The program was under active development from 2012 – 2017.

Recommended: The program was under active development from 2012–2017.

Recommended: Select a range from 10–60 px as the width of the button.

For more information, see En dashes, Hyphens, and Units of measurement.

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Suspended hyphens

Use suspended hyphens for two or more suspended compound modifiers that start with numbers.


Recommended: You can choose from either a five-, six-, or seven-sided polygon.

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In general, don’t abbreviate thousand, million, and billion as K, M, and B or k, mn and bn. Spell out the word or denote the entire number. Using these abbreviations makes it difficult to comprehend for readers and translating content.


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