Overview of number formatting
- Whole numbers and ordered events less than 10 should be written as words, not numerals (see examples), although there are some exceptions.
- Numbers with two or more digits should be written as numerals unless they are at the start of a sentence (see examples).
- Numbers between 1000 and 9999 should contain no punctuation.
- Whole numbers with five or more digits should include commas (not decimal points or full stops).
- Use ‘from’ and ‘to’ instead of a dash to describe a range of numbers in text. Numbers written out in full should be hyphenated appropriately.
- Often, judgement is needed to determine the best presentation for a set of numbers.
Examples of number formatting
Correct | Incorrect |
|---|---|
We sent the review to four referees. | We sent the review to 4 referees. |
The 10 participants agreed. | The ten participants agreed. |
The 25 studies are available. | The twenty-five studies are available. |
Thirty-three adults and five children participated. | 33 adults and 5 children participated. |
Ninth | 9th |
112th | one hundred and twelfth |
Exceptions to basic rule for numbers and ordered events less than 10
Exception | Guidance | Example |
|---|---|---|
Sentence contains numbers < 10 and ≥ 10 | Acceptable to use only numerals | from 2 to 12 years from 5% to 25% of the number of participants There were between 9 and 15 people in the room. |
Equations, numerical results, statistics | Numerals only | 2/20 OR 1.06 (95% CI 0.90 to 3.02; 6 trials, 1500 participants) (3.1% at 6 months versus 4.7% at 5 months) |
Sentence starts with a number | Spell number | Eleven per cent of people … Twenty authors attended the workshop. Eight separate doses are described. |
Number with a unit | Always use numerals | 8 mg 25 mL 6 s 0.7 kg |
Tables (see also: Tables in Cochrane Reviews) | Numerals for all numbers including those < 10 | — |
| Description of a measurement scale | Acceptable to include numeral | Outcomes were evaluated using the 9-point ORBIT classification. |
Numbers with four or more digits
Note: this is an exception to the style convention for SI units; see Units and systems of measurement.
Correct | Incorrect |
|---|---|
7677 10,000 12,100 | 7,677 10000 12.100 |
Ranges of numbers
Correct | Incorrect |
|---|---|
from three to nine participants −12 to −4 The risk ratio was 0.38 (95% CI 0.30 to 0.49) (MD −11.50 hours, 95% CI −20.04 to −2.18) 1% to 10% 4 mg to 5 mg | from three - nine participants −12 - −4 The risk ratio was 0.38 (95% CI 0.30-0.49) (MD −11.50 h, 95% CI −20.04 - −2.18) 1%-10% 4-5 mg, or 4 to 5 mg |
Number hyphenation
Rule | Correct | Incorrect |
|---|---|---|
Hyphenate compound numbers from twenty-one through to ninety-nine | ninety-seven one hundred and forty-two
| ninety seven one-hundred-and-forty-two forty three thousand and eighty-three |
Hyphenate written-out fractions | two-thirds two-fifths | two thirds two fifths |
Large numbers
Use '6.1 million' rather than '6,100,000'
Avoid 'billion' and 'trillion', due to ambiguity about their value. If they are used, they should be explained in terms of millions (e.g. '6 billion (6000 million)')
