Roman numeral converter
Convert between Arabic numbers and Roman numerals in both directions. Validates Roman numeral syntax and handles values up to 3,999.
- Free, no sign-up
- No data stored
- Reviewed 2026-01-15
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About the Roman Numeral Converter
Convert any number between 1 and 3,999 to Roman numerals, or convert a Roman numeral string back to Arabic. The converter validates proper subtractive notation.
How to use the Roman Numeral Converter
- Enter a number or Roman numeral.
- Select the conversion direction.
- View the converted result.
Frequently asked questions
What is the largest Roman numeral?
Standard notation covers 1–3,999 (MMMCMXCIX). Extensions with overlines exist for larger numbers but are not standard.
What is subtractive notation?
Using a smaller numeral before a larger one to subtract: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900.
Is IIII valid?
It appears on clock faces but is non-standard. The proper notation for 4 is IV.