#ordinal

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

A fast, fully-local number toolkit: spell numbers out in English words (great for amount-in-words on invoices and cheques), format ordinals (1st, 2nd, 112th), convert integers to and from Roman numerals (1 to 3999), convert numbers between any bases from 2 to 36, and format numbers locale-aware as decimal, currency or percent. Every endpoint accepts input via the query string or the request body. Pure server-side compute, no third-party upstream, so responses are instant and always available. Ideal for invoicing and billing, localization, education and developer formatting tooling.

api.oanor.com/number-api