In academic, scientific, and high-level business writing, the decision to use a numeral (e.g., “5”) or to spell out the word (e.g., “five”) is not a matter of choice—it’s a rule. Adhering to these conventions, set by style guides like APA, MLA, and Chicago, is essential for maintaining precision and professional credibility.
This guide outlines the most common rules to ensure your formal reports and academic papers are flawless.
The Fundamental Rule: The Rule of Ten (or Rule of One Hundred)
Most style guides adhere to a core principle that dictates the standard procedure for general numbers. This simple guideline helps create a clean reading experience, reserving figures for larger, more complex data.
- Spell Out: Numbers ten and below in most non-statistical sentences.
Example: The study involved three groups. - Use Figures: Numbers 11 and above (sometimes 101 and above, depending on the guide).
Example: We surveyed 125 participants.
Key Exceptions: When You Must Use Figures
Even if the number is small (like 5), you must always use a numeral (figure) in the following technical contexts to maintain precision:
- Measurements and Statistics: Always use figures when reporting units of measurement, percentages, fractions, decimals, or ratios.
Examples: 5 kg, 2.5 meters, 45 minutes, 4%, 2:1 ratio, 0.75. - Dates, Time, and Money: Use figures for exact dates, times with a.m./p.m., and currency amounts.
Examples: May 1, 2025, 6:00 a.m., $5 (or five dollars if the currency symbol is not used). - Page, Chapter, and Table Numbers: Use figures for locational data.
Examples: Chapter 4, Table 2, page 15. - Age: When referring to people’s specific ages.
Example: The average age was 22 years old.
Key Exceptions: When You Must Spell Out the Number
There are several scenarios where spelling out a number is required, even if it is large:
- Beginning a Sentence: Never start a sentence with a numerical figure. The number must be spelled out, or the sentence should be rewritten.
Incorrect: ~~105~~ students participated in the final phase.
Correct: One hundred five students participated in the final phase. - Common Fractions: When writing out non-technical fractions in text.
Example: “Nearly one-third of respondents agreed.” - Numbers Used as Part of a Phrase: Numbers that are used as part of a fixed, non-literal phrase (though this varies by guide).
Example: “The results were based on the rule of thumb.”
Consistency is Credibility: The Role of Your Tool
The most difficult challenge in formal writing is not knowing the rule, but applying it consistently—especially when dealing with large numbers that start a sentence (e.g., converting 1,250,500 to words).
In academic and legal documents, a single error in spelling or hyphenation undermines your authority. Our Number to Text Conversion tool is essential because it guarantees:
- Correct Spelling and Hyphenation: Eliminating common mistakes like “fourty” or incorrect hyphenation (e.g., “twenty-two”).
- Perfect Consistency: Ensuring that large numbers—which must be spelled out at the start of a sentence—are written in the exact same format throughout your paper.
Stop worrying about style rules and spelling mistakes. Use our converter to focus on your research, confident that your numbers are written with flawless professional accuracy.