Build a style guide: Numbers

It’s important to use a consistent style when writing numbers. If you’re inconsistent in the same document, it will look like a mistake!

There are various ways of writing numbers, explained below.

Style 1 is the most common – and style 2 is common in certain situations (e.g. online). The third table shows additional information on how to write numbers – which applies in most situations. Style 3 is used for writing about costs and fees in legal and financial contexts. Academic writing is covered in style 4.

Choose your style from the information in these tables:

Style 1 This is the most common style for writing numbers (e.g. newspapers, business reports, books) 
Numbers DetailsExamples
one - nine Write in wordsWe met one coach, two teachers and nine students in the gym.
10 and over Write in digitsWe met 120 students, 12 teachers and 22 parents in the gym.
Mixed numbers in the same sentenceMost common: Follow the style above so that numbers are a mixture of digits and words.
Also possible: Use all digits (which means that numbers under 10 will be digits in some sentences and spelled out in others)
a.    We met two teachers, 120 students and nine parents in the gym.
b.    We met 2 teachers, 120 students and 9 parents in the gym.
At the start of a sentenceWrite in words, even when it’s over 10 .
BUT
If the number is over 99, try to rephrase the sentence (or round it up or down)
a. Twelve people attended the meeting.

b. Last year, 102,000 complaints were made by the public.

c. Over 100,000 complaints were made by the public.
Punctuation for numbers at the start of a sentenceTwo-word numbers from twenty-one to ninety-nine are always hyphenatedTwenty-two people attended the meeting.

Style 2

Additional information Most numbering styles use these conventions 
NumbersDetailsExamples
Numbering lists Always use digits for tables of contents, page numbers, numbered lists etc.Details are in table 1 in
Appendix 2.
Million & billion• A billion is one thousand million (not one million million)

• Use the abbreviations except for people
a. €65m

b. 3bn

c. 2 million people
Units of measurementWrite in digits, even when under 102km / €4 / 1kg / 10% / 12lbs
ThousandsUse a comma for numbers over 999

Over 1,000 people attended the demonstration.
Ordinal numbers• Write out in full until ninth then use digits
• See separate entry for dates
a. First to ninth

b. 10th / 21st / 62nd
Decimals • For decimals under 1, use the zero

• Note the full stop, not a comma
a. 0.5%

b. 0.33 recurring
Avoid confusionThis is your first priority – so break any rules if it’s necessary for claritya. three 4-page reports
three four-page reports
Not: 3 4-page reports

b. the first 2 items / the first two items
Not: the 1st 2 items