Two-way · with breakdown

🏛️ Roman Numerals

Convert numbers to Roman numerals and back, up to 3,999,999 with the overline notation. Every conversion is broken down symbol by symbol, and sloppy forms like IIII are detected.

Number → Roman

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Roman → number

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Quick reference

Standard subtractive notation: I=1 V=5 X=10 L=50 C=100 D=500 M=1000; IV=4, IX=9, XL=40, XC=90, CD=400, CM=900. Numbers ≥ 4000 use an overline: a barred numeral is ×1000 (V̄ = 5000). Non-canonical input (IIII, VIIII…) is still read but flagged.