How to Present Definite Numbers and Estimations

By David Becker

Let’s take a look back at a classic guest post for our blog based on an article by Onwuegbuzie, Combs, Slate, & Frels (2010) that highlighted some of the most common APA Style errors. The number one mistake on that list is presenting numbers incorrectly. In this post, I'll be specifically focusing on how to properly present definite and estimated numbers.

According to section 4.31e of the Publication Manual (p. 112), numerals are used to represent specific values that signify time, dates, ages, scores and points on a scale, exact sums of money, and numerals as numerals. For instance, one would write 5 days instead of five days. However, there is an exception to this rule: When referring to approximate units of time (e.g., weeks, days, months, and years), use words instead of numerals, as in about five days instead of about 5 days.

You may have noticed that this is a very specific exception. You may also be wondering whether this exception applies other approximate values. The short answer is no. This exception applies only to units of time—no such exceptions apply to any other approximate units of measure. However, keep in mind that precision and clarity are key to any form of writing, especially in the sciences, so always try to present definite numbers when possible.

For more information about writing numbers in APA Style, take a look at our series of posts on numbers and metrication and our FAQ page about when to express numbers as words.