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numerosaletras.org converts numbers into words — in English, Spanish and Portuguese — for the documents where the written amount is the one that counts.
Checks, contracts, invoices and promissory notes all ask for the amount twice: once in figures and once in words. When the two disagree, the words are what binds. That makes writing them correctly worth a minute of care, and it makes a converter that gets the small rules right genuinely useful — the hyphen in twenty-one, the cents as a fraction over one hundred, the scale words that never take an "s".
The site started in Spanish, for Latin America, where the same need exists with a different set of rules. English and Portuguese followed, each written separately rather than translated, because the rules do not carry across.
The converters do not share code, because the languages do not share rules. Spanish uses the long scale, where a "billón" is a million million, and it agrees in gender and shortens "uno" before a noun. Portuguese uses the short scale and has its own rule about where the conjunction "e" belongs. English hyphenates its compounds, drops the "and" after the hundreds in American usage, and keeps its scale words singular.
Even the input is parsed differently: "1.234" is one thousand two hundred thirty-four in Spanish and one point two three four in English. Sharing a parser across the two would produce a wrong answer with no error to warn anyone.
Every tool on this site — the converters, the password generator, the word counter, the code generators — runs entirely in your browser. Numbers, text and passwords are never sent to a server, because there is no server-side processing to send them to.
That is a design choice rather than a promise about our intentions. The text people paste into these tools tends to come from documents that have not been signed yet.
The conversion rules live in plain TypeScript with a test suite that runs on every change, and the numbers used as examples throughout the site are produced by that same code rather than typed by hand. If the text and the tool ever disagreed, a reader would find out on their first attempt.
The generated spreadsheet code is checked the same way: the tests execute the JavaScript the site hands out and compare its output against the reference converter, number by number.
Everything here is free with no account and no limit. The site carries a small number of ads, which is what pays for the domain and the time. There is no paid tier, nothing is held back, and no tool asks for an email address.
Advertising and analytics cookies stay switched off until you accept them, and the converters work identically either way.
The tools here are a help, not a substitute for checking. On a check, a contract or a filing, read the amount before you sign it — the point of writing it in words is precisely that it is the version people rely on.
Questions, corrections or a rule we have got wrong: get in touch. Corrections are welcome and get acted on.