Roman Numeral Converter
Convert numbers to Roman numerals and back, from 1 to 3999, with each numeral checked against the rules and a rejected one told which rule it breaks.
Result
Result: MCMXCIV
Standard notation covers 1 to 3999; there is no zero and no negative.
- Symbol by symbol
- M 1000 + CM 900 + XC 90 + IV 4
- Standard notation
- Yes
https://calcgallery.com/notation-conversions/roman-numeral-converter-calculator/
Unit conversions follow from exact definitions and published notation rules. Sizes follow published standards and are approximate: makers grade their own, so check their chart. Figures are rounded only for display. Read the full disclaimer
How to use the Roman Numeral Converter
- Choose whether to write a number in Roman numerals or read a Roman numeral as a number.
- Enter a whole number from 1 to 3999, or a numeral in I, V, X, L, C, D and M, in either case.
- Read the result and its symbol-by-symbol breakdown. A numeral that breaks the rules is rejected with the rule it breaks.
The rules
| Symbol | I | V | X | L | C | D | M |
|---|---|---|---|---|---|---|---|
| Value | 1 | 5 | 10 | 50 | 100 | 500 | 1000 |
- Symbols are written largest first and added: MDC is 1600.
- I, X, C and M may repeat up to three times in a row; V, L and D never repeat.
- A smaller symbol before a larger one is subtracted, but only I before V or X, X before L or C, and C before D or M.
Writing a number means taking the largest value that fits, again and again, using the six subtractive pairs CM, CD, XC, XL, IX and IV along with the seven symbols. That is how 1994 becomes M, CM, XC, IV: MCMXCIV.
Reading a numeral
Add the symbols from left to right, subtracting any that is smaller than the one after it. A numeral is only valid if it is exactly how its value would be written, which catches forms such as IXI, which adds up to 10 but is written X.
With your numbers
- M 1000, D 500, C 100, L 50, X 10, V 5, I 1; a smaller symbol before a larger one is subtracted
Quick reference
Standard notation covers 1 to 3999; there is no zero and no negative.
| Example | Result |
|---|---|
| 1994 | MCMXCIV |
| 4 | IV |
| 40 | XL |
| 2026 | MMXXVI |
| 3999 | MMMCMXCIX |
| MCMXCIV | 1994 |
| IIII | |
| IC |
Common questions about the Roman Numeral Converter
- Why is 4 written IV and not IIII?
- Standard notation lets a symbol repeat at most three times in a row, and writes 4 and 9 by subtraction: IV is one before five, IX one before ten. IIII does appear on some clock faces, by tradition, but it is not standard notation, and this page rejects it.
- Is there a Roman numeral for zero?
- No. The system has no zero and no negative numbers; it was a way of writing counts and amounts, not a positional number system.
- Why does it stop at 3999?
- The largest symbol is M, 1000, and it may repeat only three times, so MMMCMXCIX, 3999, is the largest standard numeral. Larger numbers were written with a bar over a numeral to multiply it by 1000, the vinculum, which this page does not use.
- Why is IC not 99?
- Only I, X and C may be subtracted, and each only from the next two larger symbols: I from V and X, X from L and C, C from D and M. So 99 is XCIX, ninety plus nine, never IC. Many converters accept IC anyway; this one names the rule it breaks.