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Roman Numeral Converter
Convert between Roman numerals and everyday numbers. Everything happens on this page, in your browser — nothing you enter is sent anywhere.
The subtractive pairs do the heavy lifting: IV is 4, IX is 9, XL is 40, CM is 900. A smaller symbol before a larger one is taken away rather than added.
How this tool works
Roman numerals survive in outlines, clock faces, book front-matter and film credits, long after arithmetic abandoned them. Reading them is a left-to-right scan: add each symbol's value, except when a smaller symbol sits before a larger one — then subtract it.
Using it, step by step
- To convert a number, type anything from 1 to 3999.
- To decode a numeral, type it in the second box; capitals are automatic.
- Cross-check a tricky one by splitting it into thousands, hundreds, tens and ones — each place converts independently.
Where it stops
Standard form caps at 3999 because M cannot repeat more than three times without a vinculum (the overline the Romans themselves rarely bothered with). This converter follows the standard subtractive rules, so IIII — which clockmakers love — will not parse.