How Roman numeral conversion works
This calculator turns a whole number between 1 and 3999 into standard Roman numerals. It works by repeatedly subtracting the largest possible Roman value (from M = 1000 down to I = 1) from your number and appending the matching symbol, including the special subtractive pairs like IV (4), IX (9), XL (40), XC (90), CD (400), and CM (900).
These subtractive-notation rules are the modern standard used in clocks, book chapters, monarch names, and outlines. Numbers above 3999 are not shown here because the basic seven-letter system (I, V, X, L, C, D, M) cannot represent them without special overline notation.
This tool is intended for general reference and educational use.
Last reviewed August 2026