Roman Numeral Converter
Convert numbers to Roman numerals, and back again.
Result
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Convert a number (1-3999) into Roman numerals, or a Roman numeral back into a regular number, with input validation for malformed numerals.
Frequently asked questions
What's the largest number this supports?
Standard Roman numerals go up to 3,999 (MMMCMXCIX) — beyond that, the ancient system needs an overline notation this tool doesn't attempt to reproduce.
Why is 4 written as IV instead of IIII?
Roman numerals use a subtractive rule: a smaller numeral placed before a larger one is subtracted rather than added, so 4 is "one before five" (IV) rather than four ones.