Numbers
Choose between writing numbers as words or as numerals depending on the context.
Numbers as words
In general, write the numbers zero to nine as words, except as specified in Numbers as numerals.
Avoid starting sentences with numbers. Where necessary, write out the number in full. In most cases, it's better to rearrange the sentence to present the number later.
Use a hyphen when you need to write numbers that are two words, such as "twenty-four" and "eighty-five."
To make text involving multiple numbers clear, it's sometimes appropriate to change the style from words to numbers, or the other way around. For more information, refer to Multiple numbers in a sentence.
Numbers as numerals
Write numbers as numerals in the following situations:
- Numbers equal to or greater than 10.
- Version numbers.
- Decimal numbers.
- Percentages.
- Dates and clock times.
- Measurements, including prices.
- Ranges.
- Negative numbers.
- Numbers in equations and mathematical expressions.
- Values that a user must enter. Write these numbers in monospaced font.
To make text involving multiple numbers clear, it's sometimes appropriate to change the style from words to numbers, or the other way around. For more information, refer to Multiple numbers in a sentence.
Ordinal numbers
Ordinal numbers like "first," "second," and "third" indicate position in an ordered sequence. Always spell out ordinal numbers.
Don't add "-ly" to ordinal numbers.
Don't use ordinal numbers for dates. For more information, refer to Dates and times.
| Incorrect | Correct |
|---|---|
| the 1st column | the first column |
| the 25th release | the twenty-fifth release |
| secondly | Replace with a phrase appropriate to the context, such as "second," "next," or "additionally." |
Large numbers
In non-technical and non-mathematical content, large numbers are often approximate, so it's appropriate to use rounded values.
You can use a lowercase "k" to indicate thousands for large numbers without units. Don't use a space between the number and the "k."
For large numbers over 1 million, use numerals for the first part of the number, and spell out the rest.
When using a large number as an indefinite quantity, write out the number.
| Incorrect | Correct |
|---|---|
| 15 k requests | 15k requests |
| 1,000,000 | 1 million users |
| 121,000,000,000 | 1.21 billion tonnes |
| 1000s of combinations | thousands of combinations |
Negative numbers
Write negative numbers with numerals.
Use a minus sign (−) not a hyphen when you write negative numbers. Don't use a space between the numeral and the minus sign.
| Incorrect | Correct |
|---|---|
| -1 | −1 |
| − 24 | −24 |
Commas in numbers
Use a comma to separate groups of three digits in numbers that have five or more digits. Don't use spaces as separators.
exceptions
Don’t use commas to separate digits in the following situations:
- Digits to the right of the decimal point.
- Page numbers.
- Numbers in addresses.
| Incorrect | Correct |
|---|---|
| 1,00 people | 100 people |
| 1,024 bytes | 1024 bytes |
| 12345 | 12,345 |
| 100 000 | 100,000 |
| 0.3,456 meters per second | 0.3456 meters per second |
| 15 000 BC | 15,000 BC |
Multiple numbers in a sentence
To make text involving multiple numbers clear, it's sometimes appropriate to change the style from words to numbers, or from numbers to words.
If you're referring to different quantities of the same type of item, then use the same style for all numbers. If one number is 10 or greater, write all numbers as numerals.
| Incorrect | Correct |
|---|---|
| The folder contains 12 files but three of them are empty. | The folder contains 12 files but 3 of them are empty. |
Write any number that's immediately followed by a numeral as a word. For example, when discussing a quantity of something which is itself modified by a number, use words for the quantity and use numerals for the number that modifies the noun.
| Incorrect | Example of mixed numerals |
|---|---|
| 12 3-kg boxes | Twelve 3-kg boxes |
| Twenty-four files of size 70 KB | 24 files of size 70 KB |