Roman Numeral Converter
Convert modern Roman numerals and decimal integers with validation, place-value breakdowns, and copy-ready output.
Enter a decimal integer or Roman numeral, choose the conversion direction, and generate a copy-ready result. The tool runs entirely in your browser and focuses on modern Roman numerals from 1 through 3999, with an optional clock-face IIII form for four.
Use a whole number from 1 through 3999, or Roman letters I, V, X, L, C, D, and M. Unicode Roman numeral characters such as Ⅻ are accepted.
How it works
Modern Roman numerals combine seven symbols: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1000. A smaller symbol before a larger symbol means subtraction, so IV is 4, IX is 9, XL is 40, XC is 90, CD is 400, and CM is 900.
The converter validates conventional order and repetition rules, then shows a place-value breakdown so the result can be checked. For example, 1994 becomes M + CM + XC + IV, or MCMXCIV.
The supported range is 1 through 3999 because the common modern notation used here does not use overlines or other extensions for larger values. The optional clock-face setting accepts IIII where IV would normally appear, but output remains clearly marked as a clock-style variant.
