Roman Numeral Converter

The Roman Numeral Converter instantly converts between standard numbers and Roman numeral notation in both directions. Enter a number (1 to 3,999,999) to get the Roman numeral, or enter Roman numerals to get the decimal equivalent. Roman numerals remain widely used on clock faces, book chapter headings, movie sequel titles, building cornerstones, sporting event numbering (Super Bowl LIX) and royal or papal names.

The Roman numeral system uses seven symbols: I (1), V (5), X (10), L (50), C (100), D (500) and M (1000). The subtractive principle handles the values 4, 9, 40, 90, 400 and 900 by placing a smaller symbol before a larger one: IV = 4 (not IIII), IX = 9, XL = 40, XC = 90, CD = 400, CM = 900. Common mistakes include using IIII instead of IV (though IIII appears on some clock faces for aesthetic symmetry), or using VV instead of X. The year 2024 in Roman numerals is MMXXIV; the year 1999 is MCMXCIX.

The additive principle allows repetition of I, X, C and M up to three times consecutively: III = 3, XXX = 30, CCC = 300. V, L and D are never repeated. For converting large modern numbers and dates, our calculator handles millions using additional M characters. Pair with our Binary Converter for other number base conversions and our GCD and LCM Calculator for number theory problems. Free, no registration required.