How to write numbers, figures, dates and times

How good are you at watching your figures? These can be a crucial part of your document and the more clearly you express them, the better.

How you should write numbers is sometimes a matter of agreed style rather than hard-and-fast rules. So check first if your organisation has a style guide in place. If not, no problem: we’ve got you covered with our own style guidance.

Here are our guidelines for expressing time, money, statistics, data, dates and anything else involving numbers:

1. Write out numbers one to ten in words.
2. Use figures for 11 and above.
3. Avoid mixing words and figures in the same phrase. For example: ‘You can order in multiples of 9, 12 or 16’, not ‘nine, 12 or 16’.
4. When presenting data, always use figures if decimals or fractions are involved: 6.25 or 6 ¼.
5. Write ordinals (first, second, third etc) in full, not 1st, 2nd, 3rd.
6. In the body of text, write fractions in full and hyphenate them, eg two-thirds of the class.
7. Write thousands as 60,000, not 60K.
8. Use a comma for four digits or more (but not in dates): 9,000; 12,000; 5000BC.
9. Write millions as 60 million or 60m, not 60,000,000.
10. File sizes should always be written as abbreviations eg 45Kb, or 1.8Mb.
11. A billion is a thousand million (1,000,000,000), not a million million. Write billions as 6 billion or 6bn, not 6,000,000,000.
12. Use these forms rather than the 24-hour clock: 9.30am, 12 noon, 5pm, 12 midnight.
13. Write dates in this format: 7 September 2022.
14. Use ‘twenty-first century’, not ‘21st century’.
15. When indicating time span, use ‘from/to’, ‘between/and’ or ‘X–X’. But don’t mix and match: use ‘from 9am to 5pm’, ‘between 9am and 5pm’ or ‘9am–5pm’.
16. If spanning dates in the same century, drop the first two digits of the second date. But keep them if the dates span different centuries: 2017–21, 1999–2008.
17. Do not use apostrophes for collective dates: 2020s, not 2020’s.

And check out our follow-up article if you’re not sure when you need hyphens in numbers.

Image credit: andresr / iStock