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How to use Roman Numeral Converter

Type a number (1–3999) or a Roman numeral. The tool converts in the direction you edit and validates that the numeral is canonical.

Frequently asked questions

Why is the range limited to 1–3999?

Standard Roman numerals have no zero and cannot cleanly express 4000+ without overlines, so 1–3999 is the valid range.

What are the subtractive pairs?

CM=900, CD=400, XC=90, XL=40, IX=9 and IV=4 encode values just below the next symbol.

Does it reject invalid numerals?

Yes — the parser re-encodes the result and rejects any non-canonical form like IIII or IC.

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