Math, Science & Calculators · Free Tool

Roman Numeral Converter

Convert between Roman numerals and ordinary numbers in either direction — just type, and the tool detects which way you mean. Runs entirely in your browser.

Enter a number (1–3999) or a Roman numeral

Result

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How it works

If you type digits, the number is built from the standard additive/subtractive symbols (M=1000, CM=900, D=500 … down to I=1). If you type letters, each symbol’s value is summed, subtracting when a smaller symbol precedes a larger one. The result is validated by converting it back and checking it matches — so malformed numerals like IIII or VX are rejected. Classic Roman numerals cover 1 to 3999.