Roman Numeral Converter
Convert numbers to Roman numerals and back (1-3999) — instant, both directions, with the subtraction rules applied correctly.
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Invalid Roman numeral
How the System Works
Seven letters carry values — I=1, V=5, X=10, L=50, C=100, D=500, M=1000 — added left to right, except when a smaller value precedes a larger one: then it subtracts. Only six subtractive pairs are legal: IV(4), IX(9), XL(40), XC(90), CD(400), CM(900). So 2026 = MMXXVI and 1994 = MCMXCIV (M + CM + XC + IV). The classical system tops out at 3999 (MMMCMXCIX).
Where you still meet them: movie copyright years, Super Bowl and Olympiad numbering, clock faces (often with IIII instead of IV — a watchmaking tradition), monarch and pope names, book prefaces.
Frequently Asked Questions
Why is 1999 not written MIM?
Subtraction only pairs a numeral with the next one or two steps up: I before V/X, X before L/C, C before D/M. 1999 = M + CM + XC + IX = MCMXCIX.
How did Romans write zero or 4000?
They had no zero symbol. For large numbers a bar over a numeral multiplied it by 1000 (V̄ = 5000) — beyond this tool's classical 1-3999 range.
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Roman Numeral Converter