Once a Mistake, Twice, Style

The basics

In general, spell out cardinal numbers (one, two, and so on) and ordinal numbers (first, second, and so on) below 10. Use numerals for 10 and above.

Examples
Read reviews of more than 350 restaurants in your city.
Aunt Bea’s pickles won first place at the fair.
With a premium license, install the software on three computers.
Does your building have a 13th floor?

TIP

Avoid stating ordinals with superscript letters (such as 10^th, 11^th, and so on). Ordinals with superscript formatted in a word processor may not display correctly in some places, such as email. Keep your text on the same baseline: 10th, 11th.

If space is tight or if you need to emphasize a figure or a fact, use numerals for cardinal and ordinal numbers below 10, particularly in headlines, email subject lines, and HTML page titles.

Examples
In Pamplona, 8 Injured in ‘Running of the Bulls’ (Headline)
Subject: Presentation file 1 of 2 attached (Email subject line)
5th Grader Wins 1st Place in Spelling Bee (Headline)

Use numerals when referring to numbers that a person must input, for coordinates in tables and worksheets, and for parts of a document, such as page numbers or line references.

Examples
Type 5 and press Enter.
Select row 3, column 5 of the worksheet.
Refer to line 9 of the transcript.

If a passage contains two or more numbers that refer to the same category of information and one is 10 or higher, use numerals for all numbers referring to that category. When numbers are treated consistently, readers can recognize the relationship between them more easily.

Examples
The delegation included 3 women and 11 men. (Use numerals for both.)
He was the 9th person chosen for the 10-person team. (Use numerals for both.)
The most popular vote-getters included three women and nine men.
Only 3 women and 11 men attended the four-day event. (Spell out “four” because it does not relate to the same category of items as “3” and “11” do and is thus treated according to the basic rule of spelling out numbers one through nine.)

Express large and very large numbers in numerals followed by million, billion, and so forth. If expressing a number greater than 999 in numerals, use a comma.

Examples
5 billion people
1,200 years ago

Exception: Don’t use a comma with page numbers, addresses, or years—unless it’s a year with five or more digits.

Examples
Page 1026 of “War and Peace” (Page number exception)
27010 Industrial Blvd. (Address exception)
In the year 2525 (Four-digit year exception)
In 36,000 B.C. (Five-digit year)

    GLOBAL DIFFERENCES IN PUNCTUATING NUMBERS

In English-speaking North America and the United Kingdom, people use a comma in most whole numbers of four or more digits: 30,000 pounds, $1,500. But many other countries use the International System of Units, in which thin spaces are used in numbers with five or more digits: 30 000 pounds. Numbers with only four digits are expressed without a space: $1500. Furthermore, styles in the United States, the United Kingdom, and English-speaking Canada call for a decimal point: 2.5 kilos. But in continental Europe, a comma is the decimal separator: 2,5 kilos. Use the number style that’s appropriate for your location, but be aware of the differences so that you can anticipate any confusion, particularly if your website serves a global audience.

When stating million or billion with a numeral, don’t hyphenate, even before a noun. But do use a hyphen between the numeral and million or billion if the expression is part of a compound adjective that takes a hyphen elsewhere.

Examples
a $6 million lawsuit
the 400-million-served mark

If space is tight (for example, in headlines, tables, diagrams, or text messages), use the following abbreviations for large numbers:

• mil (million). See “mil.”
• bil (billion). See “bil.”
• K (thousand). See “K.” But note: Among other things, K can stand for thousand, kilobytes, kilobits, and kilograms. Use K only if its meaning is clear from the context.

Examples
Painting worth $2 mil stolen from museum
Investigators look into donations over $250K

Avoid starting a sentence with a numeral. If you can’t avoid it, spell out the number.

Example
Before
450 gamers participated in last night’s chat.

After
Four hundred and fifty gamers participated in last night’s chat.

Better
Last night, 450 gamers participated in the chat.

Exceptions:

• A year may be written in numerals at the beginning of a sentence.
• It’s OK to start a headline with a numeral if space is tight or if the numeral makes the headline more eye-catching or easier to scan or understand.

Examples
1967 was the Summer of Love in San Francisco. (Year exception in a sentence.)
8 Diet Tips (Headline exception.)
Two 5-Year-Old Boys Found; One Still Missing (Using “2” next to “5-Year-Old” would make the headline harder to read, not easier.)

If it’s necessary to spell out numbers greater than 20, use a hyphen to connect the first part of the word (ending in y) to the word following it, if any.

Examples
twenty-one
one hundred forty-three