Roman Numeral Converter
Convert numbers to Roman numerals and back, 1–3999.
Romans had no symbol for numbers above 3999 in standard notation.
Roman numerals use seven letters — I (1), V (5), X (10), L (50), C (100), D (500), M (1000). Read left to right and add the values, but subtract a smaller letter placed before a larger one, so IV is 4 and IX is 9. Standard numerals run from 1 to 3999.
How to read Roman numerals
Seven letters carry fixed values. You read them left to right and add them up — but when a smaller letter sits before a larger one, you subtract it instead. So VI is 5 + 1 = 6, while IV is 5 − 1 = 4. There is no zero, and standard notation runs from 1 (I) to 3999 (MMMCMXCIX).
The seven symbols
Every Roman numeral is built from these letters.
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1000 |
The subtractive pairs
Only I, X, and C are ever placed before a larger letter, and only before the next two sizes up. That gives exactly six valid subtractive combinations — everything else is additive.
The six subtractive pairs
Why 4 is IV, not IIII, and 90 is XC, not LXXXX.
| Pair | Value |
|---|---|
| IV | 4 |
| IX | 9 |
| XL | 40 |
| XC | 90 |
| CD | 400 |
| CM | 900 |
Worked example: writing 1994
Build the number from the largest place value down, using a subtractive pair whenever a digit is 4 or 9.
- 1 Thousands. 1994 has one thousand → M, leaving 994.
- 2 Hundreds. 900 uses the subtractive pair → CM, leaving 94.
- 3 Tens. 90 uses the subtractive pair → XC, leaving 4.
- 4 Ones. 4 is the subtractive pair → IV. Joining gives M + CM + XC + IV = MCMXCIV.
Common pitfalls
Never four in a row. A letter repeats at most three times (XXX = 30); 40 must be XL, not XXXX.
V, L, and D never repeat or subtract. They only appear once and only add — you will never see VV or IL.
Read groups, not single letters. In MCMXCIV the CM and XC are units of meaning; scanning letter by letter is where most decoding mistakes happen.
For other ways of writing the same value, see the number base converter for binary and hex, or the scientific notation converter for very large numbers.