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Numbers in the AP and Chicago Style Guides


If you’re an academic or business writer, chances are you work in different style guides regularly. Keeping each style guide straight can become confusing, especially when it comes to numbers. Here’s a helpful piece we found from the wonderfully quirky AP vs. Chicago blog!


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Numbers: Spell out or Use Numerals? (Number Style 101)


Numbers take up their own planet in the style universe, so let’s explore it one mountain at a time. This post covers the basic rules and the basic exceptions. (They’re like siblings, I tell ya.) After we get the fundamentals out of the way, we can move on to fun subcategories, such as money and measurements!


Here’s a little number warm-up to get your brains up and running.


Cardinal numbers: one, 7, forty-one, one hundred nine, 852, three thousand sixty-one
Ordinal numbers: 1st, seventh, 41st, 109th, eight hundred fifty-second, 3,061st
Arabic numerals: 1, 7, 41, 109, 852, 3,061
Roman numerals: I, VII, XLI, CIX, DCCCLII, MMMLXI


The best way to commit these distinctions to your long-term memory is to type them out and make up a string of examples for each. (Trust me.)


Note: The 2010 Associated Press Stylebook prefers the ambiguous word “figure” to refer to number symbols (e.g., 1, 2, 3), choosing to broadly define “numeral” as, among other things, “[a] word or group of words” (p. 201). I’m sticking to the definition in AP’s dictionary of choiceWebster’s New World College Dictionary—”a figure, letter, or a group of any of these, expressing a number.” The Chicago Manual of Style differentiates numerals from words as well.


Basic Number Rules (for Nontechnical Copy)


AP (p. 203):

  • Spell out whole numbers up to (and including) nine (e.g., zero, one, 10, 96, 104).
  • Spell out casual expressions: “A picture is worth a thousand words, but a really good one is worth a thousand dollars.”

Chicago (9.2-4, 9.8):

  • Spell out whole numbers up to (and including) one hundred (e.g., zero, one, ten, ninety-six, 104).
  • Spell out whole numbers up to (and including) one hundred when followed by “hundred,” “thousand,” “hundred thousand,” “million,” “billion,” and so on (e.g., eight hundred, 12,908, three hundred thousand, twenty-seven trillion).
  • Alternative rule: Spell out whole numbers up to (and including) nine, and use numerals for the rest. That’s right, you have a choice. Control yourselves, or we will make you spell out phone numbers in the 17th edition.

Numbers Beginning a Sentence


AP (p. 202): Spell out numbers that begin a sentence unless it begins with a year (e.g., “Twelve drummers,” “The 10 lords a-leaping,” “2011′s quota for off-season holiday references has been filled.”).


Chicago (9.5): Always spell out numbers that begin a sentence, or reword to avoid unwieldiness. Well, if you think that “Nineteen ninety-one” looks more awesome than “The year 1991,” then go right ahead. [Awkward silence as double bind takes effect]


Note: There is no “and” when you spell out whole numbers (e.g., “one hundred one Dalmatians,” not “one hundred and one Dalmatians”). It might be acceptable in speech, however, a grammatical deviation along the lines of “It’s me!” and “Who are you talking to?”




AP (p. 202): Spell out ordinal numbers up to (and including) “ninth” when indicating sequence in time or location (e.g., first kiss, 11th hour) but not when indicating sequence in naming conventions (usually geographic, military, or political, e.g., 9th U.S. Circuit Court of Appeals).


Chicago (9.6): Spell out ordinal numbers up to (and including) “hundredth” (e.g., second, sixty-first, 333rd, 1,024th).


A Word About Consistency


AP (p. 203): If you’re juggling a bunch of numbers within the same sentence, stick to the rules as stated and you’ll be fine. Breathe.


Chicago (9.7): If you’re juggling a bunch of numbers within the same paragraph or series of paragraphs, be flexible with the number style if doing so will improve clarity and comprehension. For example, use one number style for items in one category and another style for another category: “I read four books with more than 400 pages, sixty books with more than 100 pages, and a hundred articles with less than 4 pages.”


Now that the basics of number style have been laid out, I bet that you can smell the exceptions 1.1 miles away.


[A beat, then exit stage right]

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