Roman Numeral Converter
Turn a number into Roman numerals or read a Roman numeral as a number, with strict checking for incorrectly written numerals.
Result
Enter your values and select Calculate to see the result.
How to use this calculator
- Choose the direction of the conversion.
- Enter a number from 1 to 3,999, or a numeral using I, V, X, L, C, D and M (upper or lower case).
- Non-standard forms such as IIII or IC are flagged and the correct form is suggested.
Formula
Symbols: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000.
Symbols are written from largest to smallest and added. Six subtractive pairs are used instead of four repeats: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900).
Worked example
1994
1000 (M) + 900 (CM) + 90 (XC) + 4 (IV) = MCMXCIV.
2026
2000 (MM) + 20 (XX) + 6 (VI) = MMXXVI.
Assumptions and limitations
- Standard modern notation only; there is no symbol for zero.
- Numbers of 4,000 and above traditionally use an overline (vinculum), which is not supported.
- Clock faces sometimes show 4 as IIII; this converter treats that as non-standard.
Frequently asked questions
Why can’t I convert 4,000?
Standard Roman numerals only repeat a symbol up to three times, so MMMCMXCIX (3,999) is the largest value without special overline notation.
Is 99 written IC?
No. Only I, X and C can be subtracted, and only from the next two larger symbols. 99 is XCIX (90 + 9).