Hyphenating Numbers with Fractions

How to Hyphenate Numbers with Fractions

Here are the rules for hyphenating whole numbers and numbers with fractions.

Do Not Use Hyphens with Numbers Used as Quantifiers

When the number is a quantifier to a noun, do not use a hyphen. In these examples, the numbers are highlighted and the nouns are in bold.
• The journey takes two hours.
• The journey takes two and a half hours.
• The journey takes twenty-three and a quarter hours.
• (In this example, "twenty-three" is hyphenated because that's how 23 is written in full.)
• The journey takes 23.25 hours.
• The journey takes one and three-quarter hours.
• (Here, "three-quarter" is hyphenated because that's how a fraction is written in full.)
It doesn't matter how complicated your number is, if it's a quantifier to a noun, then it is not hyphenated. When your number is a quantifier, the only hyphens are the ones that would be there ordinarily (e.g., in numbers such as "twenty-three," "three-quarter").

Use Hyphens with Numbers Used in Adjectives

When the number is the first part of a compound adjective, use hyphens to group the whole adjective together to show it is a single adjective. In these examples, the compound adjectives that include the numbers are highlighted and the nouns are in bold.
• It is a two-hour journey.
• It is a two-and-a-half-hour journey.
• It is a twenty-three-and-a-quarter-hour journey.
• It is a 23.25-hour journey.
• It is a one-and-three-quarter-hour journey.
Again, it doesn't matter how complicated your number is, if it's the first half of a compound adjective, then it is hyphenated along with the rest of the adjective. Remember that you group an adjective with hyphens to show it's a single grammatical unit (i.e., a single, albeit multi-word, adjective). Read more about compound adjectives.

Hyphenating Terms with the Word "Year"

Writers often ask about hyphenation with terms that include "year." Here are the three main rules in the context of the word "year":

(1) Hyphenate All the Words in a Compound Noun

The term "two-year-old" is a multi-word noun (called a compound noun.) Here are some more examples of compound nouns with the term "year old" (the compound nouns are highlighted).
• A two-year-old knows its mind.
• There are three two-year-olds in the group.
• A four-and-a-half-year-old knows its mind.
• There are three four-and-a-half-year-olds in the group.
This time, there are hyphens to show that the compound noun is a single grammatical unit (i.e., a single, albeit multi-word, noun). It can happen with other words too:
• He claims to have seen a six-and-a-half-footer near the breakwater.

(2) Do Not Hyphenate a quantifier

Remember that there are no hyphens when the number is used as a quantifier, and this includes when the number quantifies the noun "year." In these examples, the numbers are highlighted and the nouns are in bold:
• She studied for four years.
• She studied for four and a half years.

(3) Hyphenate All the Words in a Compound Adjective

Numbers used in compound adjectives are hyphenated, and this includes when the compound adjective includes the word "year." In these examples, the compound adjectives are highlighted and the nouns are in bold:
• She studied for a four-year period.
• She studied for a four-and-a-half-year period.