WordBench guide
How to Write Numbers in Text: Digits, Words, Symbols and Units
Spell out zero to nine and use digits from 10 upward, always use digits with a unit, a percentage, money or a date, and never start a sentence with a digit. Large round numbers mix the two (1.5 million). The choice changes your word count: 1,250 is one word, one thousand two hundred and fifty is six.
Count your own text
The table below gives the general answer. Paste your own text here to get the exact number for it.
Numbers are the one part of a text where the reader’s eye expects a rule and notices when it is broken. Most English style guides, from AP and Chicago to the UK government’s own, land on the same core: small numbers in words, larger numbers in digits, and digits whenever the number is doing measurement work.
The rest of this guide is the exceptions and the special notations: Roman numerals, fractions and superscripts, unit symbols, money and the number-like strings that are really identifiers. Paste your own paragraph into the counter above to see how each choice changes the word and character count.
Paste this sentence into the counter: “The order of 1,250 units shipped on 3 March; twenty-one were returned, a return rate of 1.7%.” The counter reports 17 words and 93 characters, because 1,250, 3 and 1.7% each count as one word, and the hyphenated twenty-one counts as one too.
Now paste the same sentence with every number spelled out: “The order of one thousand two hundred and fifty units shipped on the third of March; twenty-one were returned, a return rate of one point seven percent.” That is 27 words and 152 characters for the same information. When a word limit is tight, digits are the cheaper choice, and they are also easier to scan.
Digits or words?
Spell out zero to nine and use digits from 10 upward. That is the AP rule and the GOV.UK rule; Chicago spells out up to one hundred in running prose, which is the main difference between the guides. Whichever threshold you pick, keep it for the whole document.
Use digits regardless of size when the number carries a unit, a percentage, a currency, a time, a date, an age, a score, a page or a version: 5 kg, 3%, 2 March, 9 a.m., page 4, version 2. Use words at the start of a sentence, or rewrite the sentence so the number is not first. Round large numbers mix the two: 1.5 million, 20 billion. Write 1,000 and above with a thousands separator in English (a comma), and keep four-digit years, phone numbers and addresses without one.
Roman numerals
Roman numerals survive where a number is a name rather than a quantity: monarchs and popes (Elizabeth II), sequels (Rocky IV), the Super Bowl, copyright years in film credits, clock faces, book front matter and outline levels. Seven letters do all the work, I V X L C D M for 1 5 10 50 100 500 1000, and a smaller letter before a larger one subtracts, so 4 is IV and 9 is IX. The year 2026 is MMXXVI.
Write them in capitals in these uses, and in lower case only for page numbers in a preface or for outline sub-levels. For any number you are not sure of, use a converter rather than counting on your fingers; romannumerals.app converts both ways, explains the rules and keeps a chart of 1 to 1,000.
Fractions, superscripts and the symbols that replace letters
Prefer the real symbol over a typed approximation where one exists. ½ is a single character (U+00BD) and reads better than 1/2; the squared in m² and ft² is a superscript two (U+00B2), not a 2; the sign in 1080 × 1350 is a multiplication sign (U+00D7), not the letter x; degrees use ° (U+00B0) and micro uses µ (U+00B5). On Windows each has an Alt code (Alt+0189, 0178, 0215, 0176, 0181) and on a Mac most sit under Option; copyglyph.dev keeps the code point, Alt code and HTML entity for every one of them.
Spell fractions out in running prose when they stand alone (two thirds of the budget) and use digits with the symbol in measurements (2½ cups). Hyphenate a spelled fraction only when it is an adjective (a two-thirds majority).
Unit symbols
The rules for unit symbols come from the SI brochure and are not a matter of house style. A space separates the number from the symbol (5 kg, 20 °C, 3 h), the symbol is never pluralised (5 kg, not 5 kgs) and never takes a full stop, and case matters: km is kilometres, but a capital K is kelvin and a capital M is mega. The percent sign is the everyday exception where most English guides close the space (3%).
Data sizes hide a second trap: kB, MB and GB are powers of 1,000, KiB, MiB and GiB are powers of 1,024, and a disk sold as 1 TB shows 931 GiB in an operating system that counts the binary way. The decimal-versus-binary bytes reference on unitglide.net lays out the two ladders side by side.
Money and the numbers that are really names
In English the currency symbol goes before the amount with no space (€20, $1,250.00), and the three-letter ISO code goes after it with a space in international text (EUR 20.00). Write cents with two decimals or none, never one, and spell out million and billion (£3.5 million).
Some strings look like numbers but are identifiers: invoice numbers, order numbers, account numbers, phone numbers. They take no separators, no rounding and no words, and they are never spelled out. An invoice number in particular has to be sequential and gap-free for tax purposes in most jurisdictions; invoicesnap.net documents the formats that satisfy those rules, such as INV-2026-0042.
Digits or words: the cases that come up most
| Case | Write | Not |
|---|---|---|
| Zero to nine, plain count | three chairs | 3 chairs |
| 10 and above, plain count | 12 chairs | twelve chairs |
| Any number with a unit | 5 kg, 3%, 2 h | five kg, three per cent |
| Start of a sentence | Twelve chairs were sold. | 12 chairs were sold. |
| Round millions and billions | 1.5 million | 1,500,000 |
| Years, phone numbers | 2026, 020 7946 0000 | 2,026 |
| Ranges | 10 to 15, or 10-15 | 10 - 15 |
| Ordinals | third, 21st | 3rd (in prose), twenty-first |
Roman numeral values
Seven letters and one subtraction rule. A smaller value before a larger one is subtracted from it.
| Number | Numeral | Number | Numeral |
|---|---|---|---|
| 1 | I | 40 | XL |
| 4 | IV | 50 | L |
| 5 | V | 90 | XC |
| 9 | IX | 100 | C |
| 10 | X | 400 | CD |
| 14 | XIV | 500 | D |
| 19 | XIX | 900 | CM |
| 24 | XXIV | 1,000 | M |
| 49 | XLIX | 2026 | MMXXVI |
Symbols to type instead of letters
| Symbol | Name | Code point | Windows Alt code | Instead of |
|---|---|---|---|---|
| ½ | vulgar fraction one half | U+00BD | Alt+0189 | 1/2 |
| ² | superscript two | U+00B2 | Alt+0178 | m2, ft2 |
| × | multiplication sign | U+00D7 | Alt+0215 | the letter x |
| ° | degree sign | U+00B0 | Alt+0176 | the letter o, deg |
| µ | micro sign | U+00B5 | Alt+0181 | the letter u |
Frequently asked questions
Should I write 10 or ten? Digits. AP style and GOV.UK switch from words to digits at 10; Chicago keeps words up to one hundred in running prose. Pick one threshold and keep it for the whole text, and use digits regardless of size whenever a unit, percentage, date, time or currency follows.
Should I write 10 or ten?
Digits. AP style and GOV.UK switch from words to digits at 10; Chicago keeps words up to one hundred in running prose. Pick one threshold and keep it for the whole text, and use digits regardless of size whenever a unit, percentage, date, time or currency follows.
Can a sentence start with a number?
Not with a digit. Either spell the number out (Twelve people replied) or rewrite so it is not the first word (In total, 12 people replied). Years are the usual exception in journalism, but even there most editors recast the sentence.
Do I write 5 kg or 5kg?
5 kg, with a space. The SI brochure puts a space between the number and every unit symbol, including °C and %. Everyday English closes the space before the percent sign (5%), and many house styles follow that one exception while keeping the space everywhere else.
How does spelling out numbers change my word count?
Every spelled-out number adds words. 1,250 is one word; one thousand two hundred and fifty is six. Hyphenated compounds such as twenty-one count as one word in this counter, and a number with a unit such as 5 kg counts as two. Paste the text above to see your actual count.
When are Roman numerals still correct?
When the number is a name rather than a quantity: monarchs and popes, sequels and events (Super Bowl LX), copyright years in credits, clock faces, front-matter page numbers and outline levels. For a measured or counted quantity, use ordinary digits.
Sources
- APA Style, numbers expressed in numerals and in words
- GOV.UK style guide, numbers
- BIPM, SI Brochure chapter 5, writing unit symbols and numbers
- romannumerals.app, how Roman numerals work (rules and chart 1 to 1,000)
- copyglyph.dev, math and measurement symbols with code points and Alt codes
- unitglide.net, decimal versus binary bytes reference
- invoicesnap.net, invoice number formats
The counting rules behind every figure on this page are written out on the methodology page, including the ones that are conventions rather than measurements.