Spell any number in words (for cheques/checks, legal documents and learning) or convert words back into a number.
Numbers • spell out
Encoding and decoding share the page, so any result can be pasted straight back to confirm it round-trips to the text you started with — the quickest check that nothing was mangled.
Results are recalculated on every keystroke, with no submit step and no page reload, so a value can be adjusted until the answer looks right rather than guessed once.
Everything runs in your browser — no account, no uploads, nothing leaves your device.
Writing numbers as words is required on cheques/checks and in legal and financial documents to prevent fraud and ambiguity — "$1,234.50" is written "one thousand two hundred thirty-four and 50/100". This converter spells any number in plain English and also converts words back into a number.
It is used for check writing, invoices, contracts, and teaching children how numbers are named. It handles decimals and negatives, instantly and privately in your browser.
Writing numbers as words is a grouping problem: split the digits into groups of three from the right, convert each group, and append the appropriate scale word — thousand, million, billion. English has irregularities that make this less mechanical than it sounds. Eleven through nineteen are special forms rather than compounds, and the tens have irregular stems. The main practical use is cheque writing and legal documents, where the written amount governs if it conflicts with the figures — which is the whole reason the convention exists.
Split into 3-digit groups from the rightConvert each group: hundreds + tens/unitsAppend scale: thousand (10³), million (10⁶), billion (10⁹)Special forms: 11–19; irregular tens 20, 30, 50where:
Assumptions: Short scale assumed, where a billion is a thousand million. The long scale, still used in parts of Europe, makes a billion a million million — a factor of 1,000 difference on the same word.
Group the digits and convert each group with its scale word.
Result"Four million two hundred seven thousand fifteen and 42/100"
The zero in the hundreds place of the final group is simply skipped rather than voiced, and the "fifteen" form is why a purely digit-by-digit algorithm fails. On a cheque, the written words are legally controlling — which is why the figures box is the one that gets altered in fraud, and the words are what banks check.
Written amounts survive damage that figures do not. A digit can be altered with a single stroke and a decimal point can vanish in a poor scan, while a word has to be rewritten to be changed — which is why cheques, contracts and statutory instruments carry the words as the controlling version and the figures as a convenience. Where the two disagree, the words normally prevail.
The conventions around that text are narrower than ordinary prose. Compound numbers below a hundred are hyphenated, so twenty-one rather than twenty one. The word 'and' marks the fractional part rather than joining hundreds to tens, which is why the American convention writes one thousand two hundred thirty-four rather than inserting an 'and' before the tens. Cents are conventionally written as a fraction over one hundred instead of being spelled out, and the line is ruled off to the right margin so nothing can be appended.
Scale names are the one place where the same word means two things. In modern usage a billion is a thousand million, but the older long scale still current in parts of Europe made it a million million — a factor of a thousand between two readings of the same word. For any document crossing that boundary, figures are unambiguous where words are not, which is the reverse of the usual advice and a good reason to include both.