Roman Numeral Converter
Convert between Roman numerals and Arabic numbers — both directions, instantly.
Free · No sign-up · Runs locally in your browser · Also available in Chinese (中文)
What is Roman Numeral Converter?
A Roman numeral converter translates between the ancient notation (I, V, X, L, C, D, M) and the numbers we use daily. The subtractive rule — IV means 5 minus 1 — is where most mistakes happen, and doing it by hand for values like 1988 is slow work.
The tool validates as it converts: malformed strings like VIIII are flagged instead of silently accepted, and numbers outside the classic 1-3999 range are rejected with an explanation, since standard Roman notation has no zero and no way to write 4000+.
How to use it
- 1Type an Arabic number to get its Roman numeral, or paste a Roman numeral to get the number.
- 2The conversion updates instantly in both directions.
- 3Check the validation message for any malformed input.
- 4Copy the result for use in documents or designs.
Common use cases
- Numbering book chapters, film sequels or annual events (Super Bowl style).
- Reading dates carved on buildings and monuments.
- Formatting outline levels in formal documents.
Frequently asked questions
▸Why can't I convert 4000 or larger?
Classic Roman notation caps at MMMCMXCIX (3999). Historical systems used an overline to multiply by 1000, but that convention is not typographically standard today.
▸Is IIII ever correct?
Clock faces traditionally use IIII for visual balance, but the subtractive standard is IV — the converter follows the standard form.