What are the guidelines for spelling out numbers?

These rules apply to American English and follow the Chicago Manual of Style, and in British English, according to New Hart’s Rules, the Oxford Style Guide.

If you’re writing fiction and following the Chicago Manual of Style (CMOS), the general rule is simple: Spell out whole numbers from zero through one hundred and use numerals for larger numbers.

If you’re writing fiction and following the Oxford Style Guide, New Hart’s Rules (NHR), the general rule is a little more detailed: Spell out whole numbers below 100, so up to ninety-nine. Here, large round numbers may be written in a mixture of numerals and words (6 million) or entirely in words (six million). If the large number is an approximation, words are preferred (about a thousand, not about 1000). If a combination of numbers is used in a sentence, it may be better to use all numerals (80 to 100, not eighty to 100).

Spelling out numbers

Spell out zero through one hundred (CMOS).

Spell out zero up to ninety-nine (NHR).

Examples:

·      After thirty days, his letter finally arrived. (CMOS) (NHR)

·      At six foot two, he towered over her. (CMOS) (NHR)

·      She was twenty-three years old. (CMOS) (NHR)

Spell out round numbers, such as hundreds, thousands, and millions (CMOS).

Large round numbers may be written in a mixture of numerals and words (6 million) or entirely in words (six million). If the large number is an approximation, words are preferred (about a thousand, not about 1000) (NHR).

Example:

·      He would have walked one thousand miles to see her again. (CMOS) (NHR)

·      There were 6 million people in the city. (NHR)

Spell out numbers that begin a sentence (though it’s often better to reword the sentence).

Example:

·      Two hundred people attended the event. (CMOS) (NHR)

Spell out times of day in even, half, and quarter hours. (CMOS)

Spell out times of day for on-the-hour only. Use numerals and a colon or period (full stop) for all other times (twenty-four-hour clock). Use a.m. and p.m. with numerals and a colon or period (full stop) for all other times (twelve-hour clock). (NHR)

Example:

·      Her day began at five o’clock in the morning. (CMOS) (NHR)

·      She arrived at 5:13 p.m. (CMOS) (NHR)

·      It was half past two when she finally put down her book. (CMOS)

·      It was 14:30 when she finally put down her book. (NHR)

Using numerals

Use numerals for 101 and above.

Example:

·      She climbed 150 steps to reach the tower’s top. (CMOS) (NHR)

Use numerals for most measurements.

Example:

·      He finished 3 miles of the race before lunch. (CMOS) (NHR)

·      The size 10 dress was a perfect fit. (CMOS) (NHR)

Use numerals when writing percentages.

Example:

·      He was 99 percent sure she felt the same way. (CMOS)

·      He was 99 per cent sure she felt the same way. (NHR)

Use numerals for dates and exact times. Note the order of day, month, year, and the punctuation used differs according to CMOS and NHR.

Examples:

·      The letter arrived on July 2, 2020, just in time. (CMOS)

·      The letter arrived on 2 July 2020, just in time. (NHR)

·      The train left at 7:20 p.m., and she barely made it. (CMOS) (NHR)

Important Exception: Jersey Numbers

CMOS specifies that jersey numbers are written as numerals, not spelled out, even if they’re under one hundred. NHR doesn’t provide specific guidelines for jersey numbers, but at KLS, we will use numerals.

Example:

·      Upon his much-anticipated return, the quarterback wore number 45. (CMOS)

·      Upon his much-anticipated return, the striker wore number 10. (NHR)

When in doubt, apply the general rules, watch for standard exceptions (such as measurements and dates), and aim for consistency.