About the Roman Numeral Converter
Convert Roman numerals (I, V, X, L, C, D, M) to standard Arabic numbers and back. The system uses additive notation (VII = 7) and subtractive notation (IV = 4, IX = 9) for compact representation. Useful for reading copyright dates on movies and TV shows, deciphering chapter headings in old books, looking up Super Bowl numbers, or doing the occasional crossword puzzle.
How to use it
- Type a Roman numeral into the left field to see the Arabic number.
- Type an Arabic number (1 to 3999) into the right field to see the Roman numeral.
- Both fields update each other live as you type.
- The converter accepts upper- or lower-case Roman letters.
Common Roman numeral conversions
| I | 1 |
| IV | 4 |
| IX | 9 |
| XL | 40 |
| XC | 90 |
| CD | 400 |
| CM | 900 |
| MCMLXXXIV | 1984 |
| MM | 2000 |
| MMXXVI | 2026 (this year) |
| MMMCMXCIX | 3999 (the maximum) |
Frequently asked questions
- Why is the maximum 3999?
- The standard Roman numeral system tops out at M = 1000, so the largest number you can spell with at most three repeated Ms is 3999 (MMMCMXCIX). Larger numbers historically used a vinculum (a bar over a letter, multiplying its value by 1000), but that notation isn't supported by plain text and isn't widely understood today.
- Is IIII a valid way to write 4?
- It's an older form. Strict modern Roman numeral rules require IV. But IIII still appears on many traditional clock faces (including Big Ben), apparently because IIII visually balances VIII on the opposite side of the dial better than IV does. The converter accepts and produces IV.
- Did the Romans really have no zero?
- Correct — the concept of zero as a number didn't exist in Roman mathematics. They didn't need it because Roman numerals are not positional — XX is twenty regardless of where the Xs sit, so there's no empty 'place' to fill. The zero as a placeholder digit was invented in India and reached Europe via Arab mathematicians around the 12th century.
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