Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers. Both boxes update live as you type, with instant validation.
Roman Value
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Number Value
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Valid Input
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Roman Numeral Reference Table
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1000 |
Subtraction Rules
- IV = 4 (5 minus 1) — a smaller symbol before a bigger one is subtracted.
- IX = 9 (10 minus 1)
- XL = 40 (50 minus 10)
- XC = 90 (100 minus 10)
- CD = 400 (500 minus 100)
- CM = 900 (1000 minus 100)
- Only I, X, and C can be used for subtraction, and each only once per position. For example, 1999 is MCMXCIX, not IMM.
How to use
- Type a whole number between 1 and 3999 in the left box to see its Roman numeral instantly.
- Type a Roman numeral (like MMXXVI) in the right box to see its number value instantly.
- Both boxes stay in sync: changing one updates the other as you type.
- Red text under a box means the input is invalid — fix it to see the result.
Tips
- Classic Roman numerals only cover 1 to 3999 — there is no symbol for zero.
- Lowercase letters are fine; the converter accepts them automatically.
- Roman numerals are still used on clocks, book chapters, and movie credits.