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How to write numbers, figures, dates and times

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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: โ€˜You can order in multiples of 9, 12 or 16โ€™, not โ€˜nine, 12 or 16โ€™.
  4. When presenting data, always use figures if decimals or fractions are involved: 6.25 or 6 ยผ.
  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 โ€˜twenty-first centuryโ€™, not โ€˜21st centuryโ€™.
  15. When indicating time span, use โ€˜from/toโ€™, โ€˜between/andโ€™ or โ€˜Xโ€“Xโ€™. But donโ€™t mix and match: use ‘from 9am to 5pm’, ‘between 9am and 5pm’ or ‘9amโ€“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: 2017โ€“21, 1999โ€“2008.
  17. Do not use apostrophes for collective dates: 2020s, not 2020โ€™s.

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

Image credit: andresr / iStock

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Kathy Gemmell

Kathy is a professional editor and one of our busiest and longest-serving trainers.

Before joining us, she spent 11 years in the publishing industry โ€“ writing, editing and commissioning illustrated reference books โ€“ as well as having stints abroad as a freelance editor and teacher.

All this experience left her with a thorough, practical knowledge of the mechanics of language โ€“ and a flair for using it. As well as running training and consulting on and editing client documents, Kathy also wrote our style guide, The Write Stuff.

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