Writing Numbers in Academic Texts: Rules & Examples
Should you write "3 participants" or "three participants"? "100 %" or "one hundred percent"? "1st" or "first"? The rules for writing numbers in academic texts are surprisingly specific, and they vary between style guides, languages, and disciplines. Getting them wrong will not ruin your thesis, but inconsistent number formatting is one of those subtle markers that separates a polished paper from a rough one. This article explains the main rules for writing numbers in academic English, covers the most common exceptions, and provides practical guidance for consistency. For automated number-formatting checks, myessay.io can scan your paper and flag inconsistencies.
The Basic Rules
Most academic style guides follow a version of the same basic rule: write out small numbers as words and use numerals for larger numbers. However, the threshold varies. APA style uses words for numbers zero through nine and numerals for 10 and above. Chicago style writes out numbers up to one hundred. Other guides have their own variations. The most important thing is to know which style your institution requires and to apply it consistently throughout your paper.
| Rule | Example (APA style) | Explanation |
|---|---|---|
| Numbers below 10 are written as words | "seven participants", "three studies" | Applies to cardinal numbers in running text |
| Numbers 10 and above use numerals | "12 interviews", "45 responses" | Numerals are easier to process in data-heavy sentences |
| Numbers that begin a sentence are written as words | "Thirty-two participants completed the survey." | A sentence should never begin with a numeral |
| Use numerals for precise measurements and statistics | "a 5-point Likert scale", "p < .05", "3.7 cm" | Precision requires numerals; words would look odd in technical contexts |
| Use numerals with units of measurement | "8 kg", "15 min", "200 ml" | Units of measurement always take numerals regardless of size |
| Percentages use numerals | "6 %", "99 %" | APA style always uses numerals with percentage, even for numbers below 10 |
| Ordinal numbers follow the same threshold | "the third chapter", "the 14th item" | Words for small ordinals, numerals for larger ones |
| Use numerals for ages, dates, and times | "5-year-old children", "March 18, 2026" | Consistency with established conventions |
Consistency Is More Important Than Memorising Every Rule
The truth is that even experienced academics occasionally disagree about number formatting. Style guides differ, disciplines have their own customs, and edge cases abound. What matters most is consistency. If you write "three factors" on page 5, do not write "3 factors" on page 12. If you use "%" in one place, do not switch to "percent" elsewhere. Pick your style guide, follow its rules as closely as you can, and apply those rules uniformly throughout the paper.
Consistent (APA style): "The survey had 12 questions. Seven of them were open-ended, and five used a 5-point Likert scale. We collected responses from 112 participants."
Note: "Seven" and "five" are written as words because they are below 10 (APA rule). "12" and "112" use numerals because they are 10 or above.
Numbers in German Academic Writing
If you are writing in German, the conventions differ in important ways. German uses a comma as the decimal separator (3,7 instead of 3.7) and a period or thin space as the thousands separator (1.000 or 1 000 instead of 1,000). The general rule in German academic writing is to write out numbers from one to twelve (eins bis zwölf) and use numerals for 13 and above, though this is a guideline rather than a strict rule. Percentages are written as "5 %" with a space before the percent sign, following DIN 5008. When writing in German, myessay.io can check your number formatting against the conventions of German academic style.
Conclusion
Number formatting is a small detail that contributes to the overall professionalism of your academic paper. The rules are not difficult — they just need to be applied consistently. Identify your required style guide, learn its number rules, and apply them uniformly. When in doubt, use the formatting that makes your text easiest to read. And for a final consistency check, myessay.io can scan your entire paper for number-formatting errors in seconds.
