Cochrane Style Manual
Numbers

In this section: Overview of number formatting | Examples of number formatting | Exceptions for numbers and ordered events less than 10 | Numbers with five or more digits | Ranges of numbers | Number hyphenation | Large numbers

Overview of number formatting

  • Numbers and ordered events less than 10 in full 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.
  • 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 five 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 h, 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


forty-three thousand and eighty-three

 

ninety seven

one-hundred-and-forty-two
one hundred and forty two

forty three thousand and eighty-three
forty three thousand and eighty three

Hyphenate written-out fractions

two-thirds

two-fifths

two thirds
two-third

two fifths
two-fifth

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)')

Section info
Describe change
Addition of new example: Description of measurement scale, e.g. the 9-point ORBIT classification.
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