Roman Numerals

How Roman Numerals works

Translate between numbers and Roman numerals, including subtractive forms like IV and CM. Everything happens inside this page: the tool reads your input, runs the calculation or conversion locally, and hands the result back to you. Nothing is transmitted, because there is no backend to transmit it to.

That design choice is deliberate. Most free tool sites upload your files to a server, process them there, and quietly keep a copy. Toolcin cannot do that — the site is a set of static files. If your connection dropped the moment the page finished loading, every tool would still work.

Seven symbols, subtractive notation

I, V, X, L, C, D and M are 1, 5, 10, 50, 100, 500 and 1000. Numbers are built by adding symbols from largest to smallest, and a smaller symbol before a larger one subtracts — IV is 4, IX is 9, XL is 40.

That subtractive rule is why 4 is IV and not IIII, and why 1999 is MCMXCIX rather than a long string of Ms.

The standard limits

Classical Roman numerals do not have a zero and are not designed for very large numbers; the converter works in the range 1 to 3999, which is where the notation is unambiguous.

Above that, overlines or a different notation were used historically — and those forms are not standardised enough for a converter to guess.

Where they still appear

Copyright years on film credits, monarchs and popes, chapter numbering, clock faces and Super Bowl numbering. In each case the numeral is decorative; nobody does arithmetic with them.

Good to know

• Works offline once loaded, including on flights and in locked-down networks.
• No file size limit beyond your device's own memory.
• Free to use, with no account and no usage counter.
• Results are produced locally, so they are not logged or shared with anyone.

Questions