Roman Numeral Converter

Roman numerals use seven letters to represent values: I (1), V (5), X (10), L (50), C (100), D (500), M (1,000). They were the standard number system of ancient Rome and remain in use today for clock faces, book chapter numbering, movie copyright dates, Super Bowl numbering, monarchs (King Charles III), and formal document outlines. Number to Roman numerals: Enter any whole number from 1 to 3,999. The converter outputs the Roman numeral with a symbol-by-symbol breakdown showing how the value is composed. Roman numerals to number: Enter a Roman numeral string (e.g., MCMXCIX). The converter validates it and shows the decimal value with each symbol's contribution. Subtractive notation rules: Roman numerals use subtractive notation for six specific combinations: IV = 4 (I before V means 5 - 1) IX = 9 (I before X means 10 - 1) XL = 40 (X before L means 50 - 10) XC = 90 (X before C means 100 - 10) CD = 400 (C before D means 500 - 100) CM = 900 (C before M means 1,000 - 100) No other subtractive combinations are valid in standard notation. The converter validates input and flags non-standard combinations. Limitations: Standard Roman numerals represent 1-3,999. Numbers above 3,999 traditionally used a vinculum (bar over letter) to multiply by 1,000 — not supported in plain text. Common conversions: IV=4, IX=9, XIV=14, XL=40, XLIV=44, XCIX=99, CDXLIV=444, MCMXCIX=1999, MMXXIV=2024.