When To Write Out Numbers in APA Style: A Comprehensive Guide

Understanding the nuances of number usage in academic writing is crucial for adhering to the American Psychological Association (APA) style. APA style provides specific guidelines to ensure clarity, consistency, and professionalism in your work. This article serves as a comprehensive guide on when to write out numbers in APA style, covering various scenarios and exceptions. By mastering these rules, you can enhance the readability and credibility of your papers.

The Basic Rule: Numbers Under Ten

The cornerstone of APA number formatting is this: generally, spell out numbers from zero to nine. This applies across the board, with some important caveats we’ll explore further below. This fundamental rule helps maintain a consistent flow and readability, especially in narrative text.

Exceptions to the Rule: When to Use Numerals

While spelling out numbers under ten is the standard, several exceptions necessitate the use of numerals (1, 2, 3, etc.). These exceptions are vital to remember, as they frequently appear in academic writing.

Numbers That Precede Units of Measurement

Any time a number is followed immediately by a unit of measurement (e.g., meters, kilograms, years, percentages, etc.), use numerals. This includes:

  • Measurements of distance: 5 kilometers, 200 miles
  • Measurements of weight: 10 pounds, 3 kilograms
  • Measurements of time: 2 years, 6 months
  • Measurements of age: 8 years old
  • Percentages: 10%
  • Scores and statistics: 3 points, a score of 8

Numbers That Represent Dates, Ages, Scores, and Points on a Scale

When dealing with dates, ages, scores, points on a scale, or other numerical designations, use numerals:

  • Dates: July 4, 2023
  • Ages of participants: Participants ranged in age from 18 to 25 years.
  • Scores on a test: The participants scored an average of 75.
  • Points on a Likert scale: Participants rated the item 4 on a 5-point scale.

Numbers That Express Ratios and Statistical or Mathematical Functions

In statistical or mathematical contexts, numerals are consistently employed:

  • Ratios: A ratio of 2:1
  • Mathematical functions: Multiply by 3, divide by 4
  • Statistical values: p < .05, t = 2.50

Numbers That Refer to Tables, Figures, or Chapters

When referencing tables, figures, chapters, or other numbered elements within your paper, use numerals:

  • See Table 3
  • Refer to Figure 1
  • Chapter 2 provides an overview

Numbers That Represent Serial Positions in a Series

If a number is used to indicate the position of something in a series, use numerals:

  • The first, second, and third items…
  • The 1st, 2nd, and 3rd examples… (Note: While “first,” “second,” etc. can be spelled out, consistency is key. Using numerals ensures uniformity.)

Consistency is Key: Avoiding Mixed Numbering

One of the most important principles of APA style is consistency. Avoid mixing numerals and spelled-out numbers within a single sentence or paragraph unnecessarily. If you use numerals for one number in a series, use numerals for all of them.

For example:

  • Incorrect: The experiment involved three trials and 4 participants.
  • Correct: The experiment involved 3 trials and 4 participants.

Or:

  • Incorrect: The researcher tested two hypotheses, one of which involved 20 participants.
  • Correct: The researcher tested two hypotheses, one of which involved 20 participants.

Numbering at the Beginning of a Sentence

This is a particularly important point. Always spell out a number if it begins a sentence. This rule trumps the general rule about numbers under ten.

For example:

  • Incorrect: 10 participants were recruited for the study.
  • Correct: Ten participants were recruited for the study.

If the number is lengthy and awkward to spell out, you can reword the sentence to avoid starting it with a number.

  • Alternative (and preferred): The study recruited 10 participants.

Ordinal Numbers: A Note on “First,” “Second,” etc.

Ordinal numbers (first, second, third, etc.) can be treated differently. While APA style doesn’t explicitly mandate spelling them out, it’s often preferable, especially in narrative text, for readability. However, as mentioned earlier, consistency is paramount. If you use numerals for ordinal numbers elsewhere in your paper, maintain that style throughout.

Complex Numbers and Compound Numbers

When dealing with complex numbers, such as those involving decimals or fractions, use numerals to maintain clarity:

  • 2.5
  • 3.75
  • 1/2

Compound numbers (numbers that combine two words, such as twenty-one) are generally spelled out when under ten, but use numerals when they are ten or greater, or when they are used with measurements, as noted earlier.

The Importance of Context: Tailoring to Your Audience

Consider your audience and the overall purpose of your writing. In some cases, especially in highly technical or scientific papers, using numerals more frequently might be appropriate for greater precision. However, in most academic contexts, adhering to the APA guidelines for number formatting will ensure clarity and professionalism.

Practical Examples: Putting It All Together

Let’s look at some practical examples to solidify your understanding:

  • Correct: The study included 6 participants.
  • Correct: The results showed a significant difference ( p < .05).
  • Correct: The participants were between 18 and 25 years of age.
  • Correct: The researchers used a 5-point Likert scale.
  • Correct: Twenty students completed the survey.
  • Correct: The experiment was replicated 3 times.

FAQs About APA Number Formatting

Here are some frequently asked questions to further clarify the nuances of APA number formatting:

1. What if a number is part of a proper noun?

If a number is part of a proper noun (e.g., “World War II”), always use numerals.

2. Can I use numerals for all numbers to be safe?

While it’s tempting to default to numerals, doing so can negatively impact readability. Follow the guidelines outlined in this article to ensure your writing is clear and professional.

3. When should I use a comma in a number?

Use commas for numbers 1,000 or greater.

4. How do I format large numbers that are spelled out?

Spell out numbers up to two words. For example, use “one hundred” rather than “one hundred and zero.”

5. Do these rules apply to all types of writing?

These rules are specific to APA style. Other style guides (e.g., MLA, Chicago) may have different guidelines.

Conclusion: Mastering APA Number Formatting

This comprehensive guide has provided a detailed overview of when to write out numbers in APA style. By understanding the basic rule, the exceptions, and the importance of consistency, you can significantly improve the clarity, readability, and professionalism of your academic writing. Remember to always prioritize clear communication and adhere to the specific guidelines outlined by the American Psychological Association. By following these principles, you can ensure your work is not only grammatically correct but also effectively conveys your ideas to your audience.