Roman Numeral Converter 🔒 Your data never leaves your browser.
Convert numbers to Roman numerals and back.
Quick reference
A few familiar numbers to check the subtractive rule (IV, IX, XL, XC, CD, CM) against.
| 4 | IV |
| 9 | IX |
| 40 | XL |
| 90 | XC |
| 400 | CD |
| 900 | CM |
| 1994 | MCMXCIV |
| 2024 | MMXXIV |
About this tool
Roman numerals are the number system used across the Roman Empire and still seen today on clock faces, movie credits, book chapters, and monarch or Super Bowl names. Built from seven letters — I, V, X, L, C, D and M — worth 1, 5, 10, 50, 100, 500 and 1000, they're combined and repeated to build any whole number from 1 to 3999, the practical ceiling of the classical system.
The tricky part is subtractive notation: a smaller letter placed before a larger one is subtracted rather than added, so IV means 4 (5 − 1) instead of IIII, and XC means 90 (100 − 10) instead of LXXXX. This converter runs both directions entirely in your browser — type a number to see its Roman form, or type a Roman numeral to see its value — with no signup and nothing sent to a server.
Frequently asked questions
Why can't I convert numbers larger than 3999?
Classical Roman numerals only define symbols up to M (1000), and the standard subtractive-notation rules stop producing unambiguous results once you'd need four or more consecutive M's — 3999 (MMMCMXCIX) is the largest number those rules can represent cleanly. Larger values traditionally used a bar over a numeral to mean "×1000", which this tool doesn't attempt to render.