Style guide

Numbers

Using numerals

Use ‘one’ unless you’re talking about a step, a point in a list or another situation where using the numeral makes more sense.

For example:  

• step 1 describes how to create your account
• write all other numbers in numerals (including 2 to 9)
• spell out numbers in common expressions like ‘one way’ - using numerals here would not make sense
• if a number starts a sentence, write it out in full (Seventeen, for example) except where it starts a title or subheading
• for numerals over 999 - insert a comma for clarity: 9,000
• use a 0 where there’s no digit before the decimal point
• use ‘500 to 900’ and not ‘500-900’ (except in tables)
• for round numbers, do not list .00 (for example £457, not £457.00)

Fractions and percentages

• spell out common fractions like one-half
• use a % sign for percentages: 50%

File sizes

• use MB for anything over 1MB: 4MB not 4096KB
• use KB for anything under 1MB: 569KB not 0.55MB
• keep it as accurate as possible and up to 2 decimal places: 4.03MB

Addresses

Use ‘to’ in address ranges: 49 to 53 Cherry Street

Numbers and accessibility

See more guidance on accessible numbers.

Last updated 01 April 2026