Friday, November 23, 2007

Writing Numbers: When to Spell It Out

When you need to specify a number in your writing, you need to decide whether to write the number out or to use numerals. Standard rules help you make that decision. Find them here.

If you use a number smaller than 100, you should write it out unless it is part of a date, time, or phone number. This rule does not apply to “o'clock” times, which should be spelled out. Thus you would write, “His plane lands at 4:23,” and, “The kids go to bed at eight o'clock.”

If you are writing about a decade or century instead of a specific date, your preference can rule. Remember, however, that you should use the apostrophe for such abbreviations as '80s and '50s at the beginning of the number to indicate that you've left off the 19.

If you can write the number with one or two words (two thousand, for example), then do so.

If the number begins a sentence, spell it out. If the number turns out to be four thousand seven hundred and twelve, re-write the sentence to use the numerals instead, 4,712.

Decimals and percentages require numbers. You should not use the percent sign, however, unless you are writing a technical paper. Spell out percent for other pieces. Common fractions should be spelled out—e.g. one-fourth, three-fifths, a third—but fractions like 13/52nds should be converted to decimals instead.

Use numerals for sentences containing a series of numbers, rather than deciding whether to use numerals or words on a case-by-case basis. Unless, that is, you are writing two numbers to modify a single noun. If you write “15 4-foot boards” readers will wonder where you find boards 154 feet long rather than what in the world you are building with fifteen 4-foot boards.

Gee, I can't understand why anyone finds these rules confusing or difficult to remember. If I've missed a rule or you still have a question about number usage, please let me know and I'll clarify or find the answer.