Write the numbers 21 to 99 with a hyphen. For example,

thirty-four

sixty-seven

ninety-nine

Hyphens are also used in larger numbers in the thousands and millions places. For example,

45,000 > Forty-five thousand

189,000 > One hundred [and] eighty-nine thousand

234,362,000 > Two hundred [and] thirty-four million, three hundred [and] sixty-two thousand

Note that American English does not use the [and] with larger numbers.

Hyphenate fractions when they are used as adjectives or adverbs. For example,

I had a one-quarter interest in the company.

Opinion varies on whether fractions used as nouns should be hyphenated.

There are no hard and fast rules although most tend to write smaller numbers in words and use numerals for larger numbers. For example,

Four

Forty-five

125

12,089

However, you should be consistent. For example,

Frank and Blake raised five pounds each but, remarkably, Sue raise £1,250.

Would be better written

Frank and Blake raised £5 each but, remarkably, Sue raise £1,250.

It is common to use the convention that applies to the larger number for all the numbers.

Alternating words and numeral forms is sometimes required for clarity. For example,

There were five eight-year-old boys at the party.

There were 5 eight-year-old-boys at the party.

Style Guides contain conventions and recommendations. They promote consistency as opposed to stating what is right and what is wrong. For example, when writing, “There was a crowd of ___ people.”, should your write “6” or “six”? What about “six thousand, five hundred” or “6,500”?

Many Style Guides are published by News media. The Associated Press (AP) guide is widely used, and you’ll find examples from it here in the Purdue Online Writing Lab. In the U.K. the BBC have their guide freely available here as do The Guardian with theirs here. Below are some examples of conventions for numbers from the AP guide alongside equivalents from another popular guide, the Chicago Manual of Style (CMoS).

Write numbers one to nine in words and use numerals for 10 and above. For example,

She worked *four* days straight.

She is due *16* days holiday pay.

Write numbers one to one hundred in words and use numerals for 101 and above. For example,

There are *thirty* days in June.

There are *365* days in most years.

Write ordinal numbers from first to ninth in words and use numerals above ninth. For example,

Sam was looking forward to his *eighth* birthday.

Nazanin came *11th* in the Spelling Bee.

Write ordinal numbers from first to one hundredth in words and use numerals beyond that. For example,

December is the *twelfth* month of the year.

The oldest person in the world just celebrated their *119th* birthday.