Roman Numeral Converter
Convert between Roman numerals and decimal numbers (1-3999) instantly.
Type in either field and the other updates automatically.
Type in either field — the other updates instantly. Supports numbers 1–3999.
Roman numerals use letters to represent values.
Basic symbols:
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1000 |
Rules:
- Symbols are generally written largest to smallest, left to right.
- When a smaller symbol appears before a larger one, it is subtracted.
- I before V or X = 4 (IV) or 9 (IX)
- X before L or C = 40 (XL) or 90 (XC)
- C before D or M = 400 (CD) or 900 (CM)
Examples:
- 2024 = MMXXIV
- 1999 = MCMXCIX
- 42 = XLII
- 3999 = MMMCMXCIX (largest standard Roman numeral)
There’s no zero and no place value here, which is what sets Roman numerals apart from the numbers we use today. The cap at 3,999 exists because there’s no single symbol for 5,000 or more. The Romans extended the system with an overline meaning “times 1,000,” but that notation almost never survives in modern use.
You run into Roman numerals more than you’d expect. They mark clock faces, the copyright year at the end of film and TV credits, Super Bowl numbers, book chapter and preface pages, and the names of monarchs and popes. One charming exception to the rules lives on clocks, where four is very often written IIII rather than IV, purely for visual balance against the VIII on the opposite side of the dial.
How we build and check this converter
This converter runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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