When should you use words (one, two, three) and when should you use figures (1, 2, 3)?
Firstly, when proofreading and copy-editing, you should always adhere to any guidelines governing numbers set out in the house style guide. If you are not given one, here are some notes to help you decide when to use words and when to use figures.
Determine a threshold
Firstly, it is standard practice to determine a threshold above which figures are used and below which words are used.
Common examples of thresholds are:
- use words for numbers below 100 (e.g. in non-technical texts)
- use words for numbers below 10 in technical texts (e.g. in technical texts)
For ZigZag Education, The Proofreading Agency’s largest client, we use the second threshold listed above: one to nine are written out and, for 10 plus, we use figures.
Remember that the threshold is meant as a general rule. There are many exceptions which are detailed below:
1. Ordinal numbers
This will depend on the context, but, in general, these should be written out.
- first, second, third, etc.
2. Large round numbers
These can be expressed as a both, or words only. Use one style consistently.
- 7 billion
- two million
3. Rounded approximations
Use words when estimating numbers in phrases such as:
- some two hundred
- about a thousand
4. Informal phrases
For informal phrases that involve numbers, use words not figures.
- she talks nineteen to the dozen
5. Lists of numbers
If a sentence contains several numbers above and below the threshold, it is generally advised to use either words or figures (not a mixture) in order to achieve consistency.
- Her girls were 6, 8 and 12 (not six, eight and 12)
6. First word in the sentence
It is generally advised not to start a sentence with a figure. Use the word or rearrange the sentence so that the figure does not fall at the start.
- Four hundred and fifty-five varieties of plant were discovered.
Use figures for the following:
- parts of books: page, chapter and line numbers (Chapter 10, page 66, line 12)
- distance (45 miles)
- scores in games (she scored 8 out of 10 in the test)
- house or building numbers (Flat 12, 18 Main Street)
- road and highway numbers (M2, A30, etc.)
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