Spelling Out Fractions

How to Spell Out Fractions

The most common convention when spelling out fractions as words is to write the top number (the numerator) as a cardinal number (e.g., three, four, five) and the bottom number (the denominator) like an ordinal number (thirds, fourths, fifths). For example:

• The population reduced by two-fifths.
(This is how ⅖ is written.)
• The population reduced by one-half.
(This is how ½ is written.)
• The population reduced by 3 and one-third.
(This is how 3⅓ is written.)

How to Hyphenate Fractions

To show the fraction as one grammatical entity and to aid reading, it is a common convention to hyphenate the numerator and the denominator (as shown in the examples above). However, when the numerator or the denominator includes a hyphen in its own right (e.g, twenty-three or twenty-thirds), then the hyphen joining the numerator and the denominator is often dropped for style purposes. For example:

• I will receive three thirty-fifths of my salary.
(This is how 3/35 is written. "Three-thirty-fifths" looks too unwieldy.)
• I will receive forty-one fiftieths of my salary.
(This is how 41/50 is written. "Forty-one-fiftieths" looks too unwieldy.)
• I will receive forty-fiftieths of my salary.
(This is how 40/50 is written. If there are no hyphens in the numerator or the denominator, then revert to the normal rules.)

Hyphenation with Fractions as Quantifiers

Another popular style differentiates between standalone fractions and fractions used as quantifiers. In this style, a fraction is not hyphenated when it stands alone but is hyphenated when it is used as a quantifier. For example:

• The population reduced by two fifths.
(Note that this is different from the most common style shown above.)
• There was a two-fifths reduction in the population.
(In this example, "two-fifths" is hyphenated because it quantifies "reduction.")

What convention should I use?

If you've come here looking for an answer on whether to hyphenate a fraction, here's your answer: It depends what convention your institution is using.

If you can't find any examples from your institution, then adopt the most common convention (i.e. the one that hyphenates fractions) and be consistent.

Why should I adopt the common convention?

• Hyphenating a fraction makes it stand out as one grammatical unit, meaning it will not hinder reading flow.
• "Two-thirds" counts as one word. "Two thirds" counts as two. So, hyphenating could be a way to reduce your word count.