Two-way · with breakdown

🏛️ Roman Numerals

Convert numbers to Roman numerals and back, up to 3,999,999 with the overline (vinculum) 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.