When to write numbers in words: APA, MLA, Chicago, UK, IEEE

Numbers in words or figures is a question every style guide answers differently. APA 7 writes zero to nine in words, Chicago everything up to one hundred, MLA whatever fits in two words, GOV.UK little beyond "one", and IEEE numbers below 11.

EdCitation publishes this guide. Its tools look sources up in the publisher's record and never write a sentence of a paper. Each rule below was read at its source in September 2026; examples marked "our example" were written for this guide, and the rest are the styles' own.

First find out which style your course wants. EdCitation's free Check your paper reads an assignment brief into a checklist that names the citation style, with the sentence each rule came from.

What is the APA rule for numbers?

APA 7 uses words for zero to nine and numerals for 10 and above, so a number under 10 is a word unless an exception applies. The American Psychological Association (2022a) gives "the study had 40 participants" and "the third, sixth, eighth, 10th, and 12th grades": ordinal numbers follow the same line.

When APA always uses numerals

Even below 10, APA uses numerals before a unit of measurement (5-mg dose, 3 cm), in statistical functions, for decimals and most fractions, percentages (50%, 75%–80%), ratios, percentiles, times and dates, approximate ones included (about 6 years ago, 12:30 a.m.), ages (5 years old), scores on a scale (scored 6 on a 7-point scale) and exact sums of money ($10) (American Psychological Association, 2022a).

After a noun in a numbered series, a number is a numeral and the noun takes a capital (Step 1, Table 2); before the noun, the ordinary rule returns (the first step, the 14th chapter).

When APA always uses words

Even at 10 and above, APA uses words for a number that begins a sentence, title or heading, for common fractions (one fifth of the class, a two-thirds majority) and for accepted phrases such as the Twelve Apostles (American Psychological Association, 2022b). Its own example mixes the forms: "Fifty percent of the students received the intervention, and the other 50% were part of a control condition." Where possible, it asks you to reword so the number does not come first.

Percentages, decimals and statistics

APA's numbers and statistics handout adds what a results section needs (American Psychological Association, 2024):

• Back-to-back numbers combine the forms: ten 7-point scales, 2 two-way interactions.
• Commas group digits in most figures of 1,000 or more, but not in page numbers, serial numbers, degrees of temperature or degrees of freedom.
• Leading zeros go before the decimal point when the statistic can exceed 1, and are left off when it cannot, as with correlations, proportions and p values: M = 0.75 but r = .45 (our example).

A whole results chapter is covered in writing up quantitative results.

How does MLA 9 handle numbers?

MLA's test is length, not size. In a paper with few numbers, spell out any that can be written in one or two words and use numerals for the rest: twenty-eight, but 101. In a paper where numbers come often, such as one built on survey results, use numerals for all of them. The Modern Language Association (2023) states both rules from sections 2.127 and 2.128 of the ninth edition.

So forty-two is a word in an MLA essay and a numeral in an APA one. Layout is in MLA 9 paper format.

MLA's other answers, from the eighth edition

The MLA posts below were written for the eighth edition, and the MLA marks each so:

• Percent or %. The symbol goes with numerals, the word with spelled-out numbers: 3.1% in statistical copy, four percent in ordinary prose (Modern Language Association, 2018c).
• A percentage opening a sentence. Reword first; if that is unwieldy, spell the first number out and keep the rest as numerals, an exception MLA allows (Modern Language Association, 2018b).
• Ranges. Write from 6 p.m. to 10 p.m., or 6 p.m.–10 p.m., never from 6 p.m.–10 p.m., because the dash stands for the whole of "from ... to" (Modern Language Association, 2018a).
• Dates. Spell out the month: 24 October 2018 or October 24, 2018 (Modern Language Association, 2019).

What does Chicago say: the general rule or the alternative rule?

Chicago's general rule spells out whole numbers from zero to one hundred, and round multiples of a hundred such as four hundred; its alternative rule spells out only zero to nine, as APA does (University of Chicago Press, n.d.-a, citing sections 9.2 to 9.4 of the 18th edition). Its editors add that numerals are the norm in scientific and technical writing (University of Chicago Press, 2023). The manual is paywalled, so this section uses only its free Q&A and blog.

Percentages, years and ordinals

Chicago prefers numerals with percentages: 10 percent in humanistic copy, 10% in scientific and statistical copy, and the number spelled out when it begins a sentence (University of Chicago Press, n.d.-c). Years take no comma up to four digits, so 2026 but 10,000 (University of Chicago Press, n.d.-d). Ordinal ranges repeat the ending (24th–25th), days of the month are cardinals (May 5–9), and spelled-out ordinals take through: first through tenth (University of Chicago Press, n.d.-b).

EdCitation builds Chicago 18 in its author-date form only, in Cite a source; the numbers rules apply to your prose either way.

How do British house styles write numbers?

There is no single British rule, only house styles, and two public ones disagree with each other.

GOV.UK

The Government Digital Service (2026) writes almost every number as a numeral, 2 to 9 included; "one" stays a word except in a step or list, as do expressions such as "one or two of them". A number opening a sentence is spelled out (Thirty-four), though not in a title or subheading. Also:

• a comma in numerals over 999 (9,000), and £138 million, with million in full;
• fractions written out (two-thirds), and a zero before a decimal point (0.5, not .5);
• % with a number, and "per cent", two words, in prose;
• 500 to 900, not 500-900, except in tables;
• first to ninth in words, then 10th;
• 4 June 2017 with no comma; 5:30pm, midday and midnight; £75.50, but £75, never £75.00.

A university writing guide: Hull

The University of Hull (2026) spells out numbers up to nine, offers "two words or fewer" as an alternative, and wants numerals in technical writing (200,000 km). It writes percent as one word, a date as "Monday 4 April, 2016" with a comma GOV.UK would drop, and money as £1.00. For a year opening a sentence, it puts "The year" in front.

In a UK essay, the department's guide or the brief decides; otherwise pick one set and keep to it. For spelling, see British or American English in academic writing.

How do IEEE and SI units treat numbers?

IEEE (2024) wants numerals with every unit, and otherwise spells out numbers below 11, one more than APA; numerals combined in a phrase stay, as in "gives 7 to 13 times more". Percentages always take the sign, repeated in ranges.

• Ranges take the unit once unless units differ (40–50 mm), and "from" pairs with "to": from 5 to 50 times.
• Spaces: an ordinary space between number and unit, and thin spaces instead of commas from five digits (62 000, but 4000).
• Dates are international: 4 June 2002. Ordinals are zeroth, first and nth, not 1st and 2nd.

The manual contradicts itself on leading zeros: its percentages section shows .25, adding the zero only for clarity, while its math rules always add it (0.25). The NIST guide to the SI takes the second view (0.25 s, not .25 s) and groups digits with a thin space, never a comma, because much of the world uses the comma as its decimal marker (National Institute of Standards and Technology, 2025). Write 0.25.

Can you start a sentence with a number?

Not as a numeral, in any of these styles. Starting a sentence with a number means spelling it out in APA, MLA, Chicago and GOV.UK, and IEEE's numerals give way there too. APA and MLA ask you to reword first, and Hull suggests the same. IEEE's one exception is the figure label: "Fig." stays abbreviated even at the start of a sentence (IEEE, 2024).

Which rules do APA, MLA, Chicago, UK and IEEE share?

Few beyond the opening numeral. "UK" is GOV.UK.

"Not confirmed" means the free pages read for this guide did not say, not that the style has no rule.

How do I get the numbers right before handing in?

Work from the brief, then read the draft once for numbers alone.

1. Find the style in the brief. EdCitation's free Check your paper lists it, with the sentence it came from.
2. Note your threshold: nine (APA, Hull), one hundred or nine (Chicago), two words (MLA), ten (IEEE).
3. Add your style's always-numeral cases: units, percentages, statistics, ages, times, money.
4. Read the first word of every sentence, heading and table title, and reword any numeral.
5. Check leading zeros, and the percent sign against the word.
6. Make each figure agree wherever it appears. Mechanics QA, in Pro, flags figures that disagree between sections.
7. Build references with Cite a source, from the publisher's record, and check them with Verify references.

Which EdCitation tools help with numbers?

Check your paper is the right first step, because the styles disagree on nearly every case and only the brief settles which you follow. Free with no account, it reads the instructions into a checklist of word limits, headings, sources, style, font, spacing and margins, each rule beside the sentence it came from.

What it returned for a brief of our own

We wrote a short brief and ran it once on EdCitation's API on 27 September 2026. It named APA 7 and gave word counts in figures and in words:

Write a report of 2,500 words (plus or minus 10%) on the survey data provided in Week 4. The introduction should be no more than three hundred words. Use APA 7th edition style for all citations and the reference list. Cite at least eight peer-reviewed sources published in the last ten years. (our example)

The rows came back as Word count, 2250 to 2750 words; Word limit · Introduction, at most 300 words, read from "three hundred"; Sources (peer-reviewed), at least 8; Source dates, "From the last 10 years"; and Citation style, "APA 7". Each row sits beside the sentence it came from, so read every row against its sentence.

Mechanics QA and Theoretics QA

Mechanics QA, in Pro at $8 a month and three checks a month with a free account, reads the whole file by rule, formatting against the APA 7 student paper included, and flags figures that do not add up or disagree between sections, such as an abstract with 124 participants and a method with 126 (our example). Each finding names the rule and the fix. It is not described as ruling on words against figures; the table above is for that. Theoretics QA, in Max at $24 a month, judges the paper against its own brief, with quotations from it. EdCitation never writes or rewrites any part of a paper, and no tool can promise a mark (pricing).

Quick questions

Is it "10" or "ten" in APA 7?

It is 10. APA 7 writes zero to nine in words and 10 and above in numerals, unless the number starts a sentence or is a common fraction.

Should I write percent or % in an essay?

APA writes 50%, MLA uses % with numerals and percent with words, Chicago writes 10 percent in humanities prose, and GOV.UK uses % with a number.

Can a sentence start with a number?

Not as a numeral. Spell it out (Forty-two participants withdrew) or reword so the number comes later.

Which EdCitation tool tells me which style my course uses?

EdCitation's free Check your paper, which reads the brief into a checklist, style included.

References

• American Psychological Association. (2022a, July). Numbers expressed in numerals. APA Style. https://apastyle.apa.org/style-grammar-guidelines/numbers/numerals
• American Psychological Association. (2022b, July). Numbers expressed in words. APA Style. https://apastyle.apa.org/style-grammar-guidelines/numbers/words
• American Psychological Association. (2024). APA Style numbers and statistics guide [PDF]. https://apastyle.apa.org/instructional-aids/numbers-statistics-guide.pdf
• Government Digital Service. (2026, June 5). A to Z style guide. GOV.UK. https://www.gov.uk/guidance/style-guide/a-to-z
• IEEE. (2024). IEEE editorial style manual for authors [PDF]. IEEE Publishing Operations. https://journals.ieeeauthorcenter.ieee.org/wp-content/uploads/sites/7/IEEE-Editorial-Style-Manual-for-Authors.pdf
• Modern Language Association. (2018a, March 14). Can you use between or from and to with a number range expressed using numerals and an en dash? MLA Style Center. https://style.mla.org/words-with-dash-in-range/
• Modern Language Association. (2018b, April 19). How do I style a percentage at the start of a sentence? MLA Style Center. https://style.mla.org/percentage-at-start-of-sentence/
• Modern Language Association. (2018c, November 14). How do I style percentages? MLA Style Center. https://style.mla.org/styling-percentages/
• Modern Language Association. (2019, January 23). What is the advantage of MLA-style date format over the format recommended by the International Standards Organization (ISO)? MLA Style Center. https://style.mla.org/mla-dates-versus-iso-dates/
• Modern Language Association. (2023, March 23). When referring to a person's age, do I use numerals or words? MLA Style Center. https://style.mla.org/numerals-or-words-for-ages/
• National Institute of Standards and Technology. (2025, August 18). NIST guide to the SI, chapter 10: More on printing and using symbols and numbers in scientific and technical documents. https://www.nist.gov/pml/special-publication-811/nist-guide-si-chapter-10-more-printing-and-using-symbols-and-numbers
• University of Chicago Press. (n.d.-a). Correct to hyphenate "four-hundredth birthday"? Chicago Manual of Style Online, Chicago style Q&A. https://www.chicagomanualofstyle.org/qanda/data/faq/topics/Numbers/faq0084.html
• University of Chicago Press. (n.d.-b). Do we repeat the abbreviation in ordinal ranges? Chicago Manual of Style Online, Chicago style Q&A. https://www.chicagomanualofstyle.org/qanda/data/faq/topics/Numbers/faq0083.html
• University of Chicago Press. (n.d.-c). In prose, when writing percentages, which is correct: 10 percent; ten percent, or 10%? Chicago Manual of Style Online, Chicago style Q&A. https://www.chicagomanualofstyle.org/qanda/data/faq/topics/Numbers/faq0005.html
• University of Chicago Press. (n.d.-d). Why do we not use commas when writing years? Chicago Manual of Style Online, Chicago style Q&A. https://www.chicagomanualofstyle.org/qanda/data/faq/topics/Numbers/faq0079.html
• University of Chicago Press. (2023, June 27). Chicago style workout 77: Numerals. CMOS Shop Talk. https://cmosshoptalk.com/2023/06/27/chicago-style-workout-77-numerals/
• University of Hull. (2026, September 9). Numbers. Writing academically, Library at University of Hull. https://libguides.hull.ac.uk/writing/numbers