Number to Words

Numbers must be written as words in several contexts: personal checks (legal requirement — the written amount is authoritative if it differs from numerals), legal documents and contracts (to prevent alteration), invoice amount lines, formal writing (style guides like AP and Chicago require spelling out numbers under 10 or 100), accessibility attributes (ARIA labels), and some government forms. The spelled-out version also helps with screen readers and voice interfaces.

English uses short-scale naming (the international standard): thousand (10³), million (10⁶), billion (10⁹), trillion (10¹²), quadrillion (10¹⁵), quintillion (10¹⁸). Each group of three digits gets a name. 1,234,567 = "one million two hundred thirty-four thousand five hundred sixty-seven". British English historically used long-scale (billion = 10¹²) but has largely switched to short-scale.

Write the dollar amount in full words, then "and" followed by the cent amount as a fraction of 100. Example: $1,234.56 → "One thousand two hundred thirty-four and 56/100". Some formats write cents as "fifty-six cents". The written line on a check is legally authoritative — if the numeral amount differs from the written line, the written line typically controls.

Cardinal numbers express quantity: one, two, three. Ordinal numbers express position or rank: first, second, third. This tool converts to cardinal form. Ordinals are formed by adding -st, -nd, -rd, or -th: 1st, 2nd, 3rd, 4th through 20th (then 21st, 22nd, 23rd, 24th, etc.). Special cases: 11th, 12th, 13th always use -th regardless of the rule (not 11st/12nd/13rd).

Compound numbers from 21 to 99 are hyphenated: twenty-one, thirty-two, ninety-nine. Numbers with "hundred" or larger units are not hyphenated in most style guides: five hundred, one thousand. However, "a hundred and twenty-three" hyphenates the 23. The AP Stylebook and Chicago Manual of Style agree on hyphenating 21–99 but differ on other details.