Number Words API
Format numbers in human-readable forms as an API. Spell any number in English words — handling thousands through quintillions, negatives and decimals (e.g. 1,234,567 → "one million two hundred thirty-four thousand five hundred sixty-seven", 12.56 → "twelve point five six"). Turn a whole number into its ordinal, both short (21 → 21st, 113 → 113th) and written out (twenty-first, one hundred thirteenth). And convert any whole number from 1 to 3999 to Roman numerals and back (2024 ⇄ MMXXIV), with strict validation. Everything runs locally, so it is fast and always available. Ideal for invoices, cheques and accounting, legal documents, internationalisation, accessibility (screen readers), education and any UI that turns digits into words.
api.oanor.com/numberwords-api
