Should FixStyleFound in 1-2% of dissertations

Chicago Number Spelling: The 0-100 Rule That Differs From Every Other Style

Found in 1-2% of dissertations using Chicago style. CMOS requires spelling out numbers zero through one hundred — a wider range than APA and a different threshold than MLA.

FIX

Spell out whole numbers from zero through one hundred.

What This Issue Is

Chicago Manual of Style spells out whole numbers from zero through one hundred, as well as certain round numbers: two hundred, three thousand, one million. Use numerals for 101 and above (except round numbers) and for any number that would be awkward to spell out. So it's "ninety-nine participants" but "102 participants," and "three thousand respondents" but "3,247 respondents."

This is the broadest spell-out rule of the three major styles. APA spells out zero through nine. MLA spells out numbers expressible in one or two words. Chicago goes all the way to one hundred. If you've been writing in APA and switch to Chicago, you'll need to spell out far more numbers than you're used to — "twelve," "forty-five," "ninety-eight" all get written as words.

The exceptions follow common sense. Use numerals for percentages (55%), decimals (3.5), statistics, measurements with units (7 cm), page numbers, and numbers in tables or figures. When you have a series of numbers in the same sentence and some fall above and below the threshold, you can use numerals for all of them for consistency: "we surveyed 45, 78, and 120 participants across three sites."

Why Your Committee Flags It

Chicago recommends spelling out numbers zero through one hundred in humanistic contexts. Scientific contexts may use numerals more freely, but consistency is key.

Before & After Examples

Before

The program served 45 students over 12 weeks.

After

The program served forty-five students over twelve weeks.

Both 45 and 12 fall within Chicago's 0-100 spell-out range.

Before

The study included 45 teachers from 12 schools.

After

The study included forty-five teachers from twelve schools.

102 is above the threshold — use the numeral. Restructure to avoid starting with a number.

Before

One hundred and two students completed the pretest.

After

A total of 102 students completed the pretest.

Non-round numbers above 100 use numerals in Chicago. Only round numbers spell out.

Before

The district employed three thousand two hundred forty-seven staff members.

After

The district employed 3,247 staff members.

Self-Check Checklist

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Frequently Asked Questions

Spell out whole numbers zero through one hundred and certain round numbers (two hundred, three thousand, one million). Use numerals for 101 and above (except round numbers) and for decimals, percentages, statistics, and measurements. When in doubt, the Chicago Manual of Style's online Q&A has specific guidance.
APA: spell out 0-9, numerals for 10+. MLA: spell out numbers expressible in one or two words. Chicago: spell out 0-100 plus round numbers. Chicago is the most extensive spell-out rule. If you switch styles, the number rule is one of the biggest formatting changes you'll face.
In Chicago, spell it out: 'one hundred.' The rule covers zero through one hundred inclusive. Use numerals starting at 101. The round-number exception means 'two hundred' and 'three thousand' are also spelled out, but '101' and '350' use numerals.

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