How to Write Numbers using APA Guidelines

The Number Game

Knowing when to use the Arabic form of a number (the actual number) or when to write the number out can be confusing. The general APA (American Psychological Association) rule of thumb is to write out any number under 10 and use the actual number if it is over 10, but there are exceptions to this rule and if you are writing for publication or a school assignment, it is good to know these exceptions. This article will help you know how to state a number when you are writing.

Instructions

1. Numbers Expressed as Figures (sometimes called the Arabic form of numbers). In general, you should write all numbers 10 and above as figures and all numbers less than 10 as words. Examples: "There are 13 prizes in the contest." Or "The stick was 12 cm long." You also need to write all numbers that are grouped for comparison with numbers 10 and above as figures. Examples: "They were tested in the 3rd and 12th grade and the 3rd grade students did much better." Or "When reviewing responses, 2 of 20 were identical." Numbers that immediately precede a unit of measurement, like "A 5-mg dose..." Or "It was a 12 inch ruler." You will also use figures to express numbers that represent time, dates, or ages. For example, "In about 3 years." Or "There were several 2-year-olds at the party." Finally, all numbers that represent a specific place in a numbered series, parts of books, and every number in a list of four or more numbers. Examples: "Table 3; Page 71; Chapter 5; Row 2; 1,4,5, and 7 respectively."

2. Exceptions to the rules above: numbers written as words. If a number below 10 does not represent a specific measure or are grouped for comparison with other numbers below 10. Examples: "He repeated the task three times." Or "Two words that mean the same thing." Or "It happened at five of the remaining seven trials." Another exception to the rule of figures vs.. words is when the number appears as the first word in a sentence. "Ten participants in the contest..." Or "Forty-eight percent showed no change, however 2% showed an increase." Or "Four students won the contest and 4 lost." Whenever possible, re-word the sentence so the first word is NOT a number to avoid any confusion.

3. Writing numbers as mathematical expressions is almost always done in Arabic format. When writing decimal fractions, include a zero before the decimal point if the number is less than 1. Example: 0.25 inches or 0.58 inches. Roman Numerals should always be written as Roman Numerals if they are part of the established terminology. For example, if the term is Type II Error, do not change it to the Arabic form (Type 2 Error). Generally use Arabic numbers for routine lists, etc. Example: Step 1, Step 2, etc.

4. Commas in numbers can be confusing, so as a general rule always use commas between groups of three digits in most figures of 1,000 or more. Of course, there are exceptions to this rule: page numbers (page 1038); binary digits (00011011100); serial numbers (258974631); degrees of temperature (3084◦ F); numbers to the right of a decimal point (4,987.2598).

5. Plurals of numbers. This one is probably the most abused rule. If a number is written as a plural, do NOT use an apostrophe when adding the s or es: fours and sixes, 1950s, 10s and 20s. When referring to an era (the 1950s) the year is plural, not possessive and there is NO apostrophe.

Tips & Warnings

• There are many other rules and exceptions to those rules, but if you follow these basic steps when writing numbers you can't go wrong.

• When in doubt, follow the most general rule: Numbers less than 10 are spelled out, 10 and higher are written in figures.

• Keep in mind the rule for apostrophes for numbers expressed as plurals. NO APOSTROPHE. An Apostrophe is meant to show possession, not plurality.