Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers.
About the Roman Numeral Converter
Roman numerals still show up on clock faces, book chapters, movie credits, monuments and the Super Bowl. The AlarmDaddy Roman Numeral Converter turns any whole number from 1 to 3999 into its Roman form, and converts a Roman numeral back into an ordinary number. Type in one side and read the other instantly.
Roman numerals use seven letters — I, V, X, L, C, D and M — combined with a simple subtractive rule, so 4 is IV (one before five) and 9 is IX. The converter validates what you type, so a malformed numeral like IIII or VX is rejected rather than silently misread. The classic system only represents numbers up to 3999, which is the range this tool covers.
How to use this calculator
- 1Choose the direction: number to Roman, or Roman to number.
- 2Type a number from 1 to 3999, or a Roman numeral.
- 3Read the converted result instantly.
The formula
Values are added left to right, except when a smaller symbol precedes a larger one (IV, IX, XL, XC, CD, CM), where it is subtracted. The converter builds numerals greedily from the largest value down, and validates Roman input by converting it back and comparing.