How to use
- Type a number from 1 to 3999 into the left field — the Roman numeral appears instantly.
- Or type a Roman numeral into the right field (case does not matter) to get the number.
- Check the part-by-part breakdown and copy the result with the button.
FAQ
Why are IIII or VX rejected?
In standard notation a symbol repeats at most three times in a row (III, but 4 = IV), and V, L and D are never repeated or subtracted. So IIII, VV and VX are invalid. The converter shows the correct form when it can be determined.
Which pairs can be subtracted?
Only six: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). Forms like IC for 99 or IL for 49 are not used: 99 = XCIX, 49 = XLIX.
Why is the maximum 3999?
Without special marks the largest number is MMMCMXCIX (3999). Larger numbers were historically written with a bar over a numeral (times 1000). You can enable that mode with the checkbox to go up to 3,999,999.
Is there a zero in Roman numerals?
No. Roman numerals have no symbol for zero or negative numbers, so the converter accepts numbers starting at 1.