I had a query from a client the other day asking why sometimes I used the words for numbers (e.g. eight) and sometimes I used the numerals (e.g. 16). Here are the generally accepted basic rules about which to use when.
If the number is between one and ten, use words.
She was eight years old.
He ran seven miles that day.
If the number is over ten, use numerals.
She was 16 years old.
He ran 14 miles that day.
Keep to this format, even when there is a mixture of words and numbers in a sentence.
He ran three miles on Saturday and 13 miles on Tuesday.
(N.B., some style guides say to switch to numbers at ten, so you would say ‘She was 10 years old’. My preference is to use words up to ten and use numbers from 11 onwards.)
However, if the number is at the start of the sentence, use words, no matter how big the number.
“Two pounds of apples, please.”
“Seventeen punnets of strawberries, please.”
The exception to this rule is when you’re describing a year.
1805 was the year the Battle of Trafalgar took place.
(Although I always think this looks slightly awkward and try to reword to avoid having the number at the start. ‘The Battle of Trafalgar took place in 1805’.)
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