Spelling out numbers

When do you spell out numbers and when do you leave them in numeral form? How do you know where to put the pesky hyphens?

Your mileage may vary based on house style, but here are some guidelines to get you started.

How to spell out numbers:

• - Hyphenate all numbers between twenty-one and ninety-nine, even if they’re part of a larger number (three hundred twenty-one) or if they’re ordinal (twenty-first, ninety-ninth). Do not hyphenate hundreds or thousands (three hundred, five thousand).
• - Some stylesheets recommend an “and” (three hundred and twenty-one), others say it’s optional. Still others say that “and” should be reserved to represent a decimal point. Always check and obey the style guide for your particular publisher or project.
• - Hyphenate simple fractions, such as one-fourth or two-thirds. In the case of whole numbers with fractions, hyphenate only the fraction (two and one-third).
• - If a number is part of a compound modifier (two words used as a single adjective), it should be hyphenated, whether written out or not (a two-foot gap, a 40-watt bulb, the third-floor apartment or fifth-to-last contestant).

Consistency and readability are the most important considerations when spelling out numbers. In general, numbers used for technical purposes will almost always be in numeral form. In non-technical context, numbers less than ten (or less than one hundred), round numbers, numbers in dialog and numbers that begin a sentence will be spelled out.

When multiple numbers of similar units occur in the same sentence or paragraph, be consistent in how they are handled. It may be technically correct to say “Of the 35 students, three were absent,” but it’s more consistent and readable to choose one way to handle the numbers of students and stick to it through the sentence.

When to spell out a number:

• - At the beginning of a sentence. If it’s awkward to do so, recast the sentence so that it doesn’t begin with the number. (Change “Eighteen seventy-five was the year in which…” to “In the year 1875…”)
• - When a number is less than ten (alternately, less than one hundred, based on style preference).
• - When a number is round, whether used precisely or as an approximation (there were about eight hundred people at the concert).
• - When used in dialog, within reason.
• - For simple fractions (a three-fifths majority).
• - For time of day, when o’clock is used. Always spell out the time if you’re using o’clock.
• - For government, military, political and religious units, ordinal numbers up to one hundred are spelled out (Fifth Division, Fourth Precinct, Eighth Dynasty, Third Church of Christ).

When to use a numeral:

• - Highways are never spelled out (Route 101, or the M1).
• - Street addresses (Unless the address is One, which is sometimes spelled out for clarity).
• - Exact times of day (6:22) with exceptions for “noon” and “midnight”.
• - A particular year (1875), except at the beginning of a sentence.
• - Legal and financial instruments and documents (401(k), Chapter 11).
• - Biblical references and scholarly citations.
• - Very large numbers including large amounts of money (2.3 billion) or specific amounts of money ($55.32). If using a currency symbol, always use numerals (“$4 million dollars” is fine, but never “$four”).
• - Percentages are always written in numerals.
• - Numbers less than zero are always written in numerals.
• - Page numbers are always written in numerals.
• - Trademarked and proper names that are spelled with numbers should always be written with those numerals.

Gray areas that are more likely to depend on a particular author or publisher preference:

• - Day of the month
• - Decades and centuries
• - Dates
• - Numbers between ten and one hundred

Also worth noting:

• - Decades and centuries are not capitalized (the eighteen hundreds, the nineteenth century).
• - The plurals for spelled out numbers are formed with the same rules as other nouns.
• - The plurals for numerals are formed by adding ‘s’, without an apostrophe. This includes years and decades.

Tagged as: grammar