Most of the time, use ‘one’ rather than ‘1’.
✔ We built one new school this year.
In some cases, using ‘1’ makes more sense.
✔ In step 1 of the instructions...
Spell out a number when it begins a sentence
✔ Eight people entered the building.
Write all other numbers as numerals
✔ There were 8 people in the building.
The same rules apply to ordinals
✔ First, he answered the 2nd question.
Keep expressions that normally use spelled-out numbers unchanged
✔ This started a third-party investigation.
✔ They bought a second-hand car.
For numerals over 999 use commas
✔ 3,000,000
Do not use ‘k’ to abbreviate thousands
✔ £400,000
❌ £4k
Use a 0 when there’s no digit before a decimal point
✔ 0.25
❌ .25
Write out and hyphenate fractions
✔ one-half
Use % for percentages
✔ Turnover increased by 60%.
❌ Turnover increased by 60 percent.
Use 'to' in ranges
✔ There will be 500 to 900 spectators.