Numbers in Academic Writing – APA Style Guidelines

01.01.23 Academic language Time to read: 4min

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Are you writing an APA style paper and wondering how best to represent numbers within the text or references?

This guide will outline exactly how to write numbers within your paper and the general rules you should follow.

Our guide is broken into useful sections that cover every aspect of using a number, from percentages to in-text ordinal numbers.

Numbers in Academic Writing – In a Nutshell

  • Academic writing uses numbers in distinct ways depending on the discipline and writing style.
  • Conventions apply to technical number writing, like mathematics and the sciences, and non-technical number writing, like academic prose.
  • Numbers should usually appear written out from one to nine, with numerals used from 10 onwards.
  • Technical data and statistics should always appear as numerals for reference.

Definition: Numbers in academic writing

The APA Style is one of the most widely used academic writing styles and is largely adopted by the behavioral and social sciences. A number can be written both numerically or in words within this style.1

Typically, a number from one to nine should be written out as words, while numbers from 10 and above should be written out numerically. This general rule also applies to ordinals (first, 10th). Some exceptions do apply, as found next in this article.

Other writing styles utilize different number rules. The Chicago Style, for instance, requires numbers to be written out as words up to 100. The MLA Style spells out all numbers that can be written within one or two words (three, one hundred, etc.).2

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Numbers in academic writing: Exceptions

Exceptions to the general rule above apply in the following cases:

1. All numbers should be represented numerically when they are detailing an exact unit of measurement.


  • The rock was chiseled 6 cm deep.

2. Write out numerals as words when they begin a sentence, except when dealing with specific years.


  • Eighteenth-century scientists advanced the practice of medicine
  • 1921 marked the discovery of insulin.

3. A number should be written out when dealing with fractions, set expressions, or other known numeric titles.


  • John Milton crafted his Gunpowder Plot poem in 1626, erroneously referred to as the Fifth of November poem.
  • According to the literature, one-third of the English population perished from the Black Death.
  • Orwell’s Nineteen Eighty-Four is set in an alternative world in the year 1984.

Numbers in academic writing: Percentages

When dealing with percentages in the APA Style, use numerals followed by a % symbol, instead of “percent”.3


  • The Spanish flu affected over 25% of the US population.

The previous rule applied to sentences beginning with numerals also applies to percentages, meaning that percentages should be written out as words when they start a sentence.


  • Twenty-five percent of the US population was affected by the Spanish flu.

Numbers in academic writing: Statistical results

Reporting statistics in APA and papers that deal with technical numerical language in qualitative research have their own rules.

Here, all data is written in numerals to remain consistent and easily digested. This applies to the main body, tables, and figures sections of a paper.

Other statistical conventions include:

  • Report the majority of statistics to two decimal places.
  • Report statistics that can’t exceed 1.0 to three decimal places.
  • For values that could exceed 1.0, use a leading zero. Those that can’t exceed 1.0 do not feature a leading zero.
  • Italicize statistical values that aren’t Greek letters. E.g. SD.
  • Spaces should be left before and after equal, more-than, and less-than signs.

Numbers in academic writing: Measurements

Always use numerals for units of measurement.


  • Ampules contain 100 mg in 2 ml.

Numerals should be used for precise ages, timescales, dates, score lines, points of scale, and monetary sums.


  • The final score of France 4, and Croatia 2 meant that France won the World Cup.
  • Students aged 18 to 21 years receive a £10 discount.

Imprecise ages and generalizations are not numbered but written.


  • She was roughly six years old.
  • She was 6 years old.
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Numbers in academic writing: Long numbers

Longer numbers have their own set of rules. A period should be used to indicate a decimal point.

Commas are to be used to separate large figures every three digits after 1,000.

For sums exceeding 6 numerals, like 1 million and 1 billion, use a combination of numerals and written language.


  • HBO Max had 73.8 million subscribers in 2022.
  • This is a considerable growth from its 800,000 subscribers in 2015.


As a general rule of thumb, numbers up to nine should be written out in the APA Style, while anything exceeding 10 should appear as numerals.

Dates are always written as numerals.

They are written out when they begin a sentence, except for dates and technical data.

The APA Style states that the symbol “%” should be used after numerals, while “percent” should be used for written-out figures.


1 Purdue Online Writing Lab. “Numbers and Statistics.” Purdue University. Accessed December 8, 2022.

2 Becker, David. “APA Style 6th Edition Blog: Comparing MLA and APA: Numbers.” APA Style Blog. June 26, 2014.

3 Hutchison, Katie. “How Do I Report Small Percentages (Less than 1%) Using APA Format? – LibAnswers.” Brother Edmond Drouin Library. September 1, 2016. Accessed December 8, 2022.