Roman Numeral Converter

Roman numerals use letters: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Read left to right adding values. When a smaller numeral precedes a larger one, subtract it: IV=4 (5-1), IX=9 (10-1), XL=40, XC=90, CD=400, CM=900. Example: 2024 = MMXXIV = 1000+1000+10+10+4.

Standard Roman numerals go to 3,999 (MMMCMXCIX). For larger numbers, a bar over a letter multiplied by 1,000: V-bar = 5,000, X-bar = 10,000, M-bar = 1,000,000. This is called vinculum notation and allows representation of millions.

Maximum 3 of same symbol in a row (III is valid, IIII is not — use IV). Subtraction: only I before V or X, X before L or C, C before D or M. Never subtract more than one symbol at once (not IIX for 8 — use VIII). Symbols decrease in value from left to right (except subtractive pairs).

Clock faces (some use IIII instead of IV). Movie copyright dates and sequel numbering (Rocky IV). Super Bowl and Olympic Games numbering. Chapter numbers in books and outlines. Building inscriptions. Monarchs and popes (Henry VIII, Pope Francis I). Astronomy (planetary moons: Io, Europa, etc. are Jupiter I, II).

Roman numeral systems developed as a counting notation — tallying quantities that exist. Zero represents the absence of quantity, which was not needed for Roman commerce or administration. Zero was developed independently in ancient India and the Maya civilization. Arab traders brought Indian zero to Europe in the Middle Ages.