Number Style Checker
Paste a draft and pick APA 7 or Chicago 18 to see every number that breaks the style's general rule: a numeral that should be a word, a word that should be a numeral, a number that opens a sentence, a percent in the wrong form, and a number missing its unit. Each flag names the rule and gives the replacement. Free, no sign-up.
Runs entirely in your browser — your text is never uploaded.
Paste or type some text to check which numbers should be words and which should be numerals.
How to Use the Number Style Checker
- Pick the style. APA 7 is the default for psychology, education and most social sciences. Chicago 18 is the general rule for history and the humanities.
- Paste your text. A results section or a whole paper works. Quoted text is skipped unless you untick the option, because a quotation keeps its original numbers.
- Read the colours and the table. Each highlight names the rule it breaks: blue for a numeral that should be a word, amber for the reverse, rose for a number that opens a sentence, violet for percent, green for a number with a unit. The table gives the replacement.
- Judge the flags. The checker reads patterns, not meaning. A score, a statistic or a label can look like a count, so confirm the rule applies before you change a number.
The Two Rules in One Table
The two manuals set the line in different places. APA 7 (Publication Manual §§6.32–6.39) writes zero through nine in words and 10 and above in numerals. Chicago 18 (chapter 9) writes zero through one hundred in words, plus round multiples of those numbers such as two hundred, fifty thousand and 3 million, and uses numerals for the rest. AP style also uses numerals from 10, but its exceptions differ from APA's, and this tool does not check it.
| You mean | APA 7 | Chicago 18 |
|---|---|---|
| 5 apples | five apples | five apples |
| 12 apples | 12 apples | twelve apples |
| 101 apples | 101 apples | 101 apples |
| a sample of 5% | 5% | 5 percent |
| 5 minutes | 5 minutes | five minutes |
| 5 kilometres (abbreviated) | 5 km | 5 km |
| the 21st century | the 21st century | the twenty-first century |
| 3 million people | 3 million people | 3 million people |
| a number that opens a sentence | spell out or reword | spell out or reword |
What APA Always Writes as Numerals
APA's exceptions to the nine-and-ten rule matter more than the rule. Use numerals, whatever the size, for numbers before a unit of measurement (a 5-mg dose, 3 cm), statistics and percentages (5%), times and dates, including approximations (approximately 4 months, 2 years), ages (7 years old), scores and points on a scale, exact sums of money, and numbers that follow a noun in a series (Table 3, Step 1, Grade 5). Use words, whatever the size, for a number that begins a sentence, title or heading, for common fractions (one-half, two-thirds) and for fixed phrases such as Twelve Apostles. The APA Style number pages set out the full list.
What Chicago 18 Adds
In non-scientific text Chicago spells out percent after a numeral (5 percent), writes a number with a spelled-out unit in words (five kilometers) and one with an abbreviated unit in numerals (5 km), and spells out ordinals and centuries (the twenty-first century). In scientific and technical contexts it allows numerals throughout and the % symbol; the checker applies the general, non-scientific rule. Chicago also asks for numerals throughout a passage when numbers on both sides of its threshold are being compared; the checker does not enforce that.
What the Checker Skips
- Contexts both manuals keep as numerals: decimals, fractions and ratios, times and dates, years, page and table references, statistics (n = 5, p = .03), ranges (3–5), money with a symbol, and numbers attached to an abbreviated unit.
- Labels and names: a number after Table, Figure, Step, Chapter, Grade, Phase, Study and similar nouns, after a capitalised word or acronym (APA 7, Apollo 11), and in lists of numbers (1, 3, 5) or bracketed indexes (91(1)).
- Text that is not yours: quotations, citations with a year, page citations, URLs and DOIs, headings and list markers.
How Accurate Is It?
The rules are fixed, so the test is whether they match what an editor would say. On 64 hand-labelled passages they did, and on 29 more written afterwards and run before tuning, 28 of 31 matched at first. One miss was a real bug (9 in May was read as nine inches), and two were my labels being wrong, so those two passages were dropped. Real prose is harder. On roughly 8,300 numbers in this site's own guides, which are heavy with editions, volume numbers and citations, the APA setting flagged about 4 in every 100. Most were genuine (9th edition should be ninth edition in APA), and the false alarms were class years, report codes and similar. Treat the flags as a proofreading list, not a verdict.
Worked Example
The Try an example paragraph has 54 words and 14 numbers, 10 as numerals and 4 in words. APA flags 8 of them; Chicago flags 7. Both flag the two sentence-opening and single-digit numerals, and both leave Table 3, n = 40 and January 1, 2001 alone. They disagree on the rest:
Original
The test lasted five minutes, and 25% of students scored above the mean.
APA 7
The test lasted 5 minutes, and 25% of students scored above the mean.
Chicago 18
The test lasted five minutes, and 25 percent of students scored above the mean.
Original
The 21st century began on January 1, 2001.
APA 7
The 21st century began on January 1, 2001.
Chicago 18
The twenty-first century began on January 1, 2001.
Frequently Asked Questions
- What is the APA rule for numbers?
- Write zero through nine in words and 10 and above in numerals. The exceptions are numbers that always take numerals (measurements, statistics, percentages, times, dates, ages, scores, exact money and numbers after a noun, as in Table 3) and numbers that always take words (one that begins a sentence, title or heading, and common fractions).
- Can I start a sentence with a number?
- Both APA and Chicago say to spell it out, and to reword when that is awkward. Twelve students left is fine; 2019 was a wet year is better as The year 2019 was wet or In 2019, it rained all year. The checker offers the spelled-out form for ordinary numbers and asks you to reword a year or a decimal.
- Is it 5% or 5 percent?
- In APA, a percentage takes the symbol with a numeral: 5%. In Chicago's non-scientific text, write a numeral and the word: 5 percent. Use the word percent on its own, without a numeral, in running text in either style.
- Why does the checker want “5 minutes” in APA but “five minutes” in Chicago?
- APA writes numbers before units of measurement and time as numerals, whatever their size. Chicago's general rule spells out numbers from zero through one hundred, and treats a spelled-out unit like any other noun. Chicago keeps numerals only with an abbreviated unit, such as 5 km or 10 min.
- Do ordinals follow the same rule?
- Yes. APA spells out first through ninth and uses numerals from 10th, so the 3rd trial becomes the third trial and the twelfth trial becomes the 12th trial. Chicago spells out ordinals up to one hundredth, which is why it wants the twenty-first century.
- Does it check AP style or MLA?
- No. AP spells out one through nine and uses numerals from 10, but its exceptions differ from APA's. MLA's general rule is closer to Chicago's. Switch to the style your instructor names, and check any flag you are unsure of in their handbook.
- Is my text uploaded anywhere?
- No. The checker runs entirely in your browser; nothing you paste is sent to a server or stored.