Roman Numeral Converter
Convert any number between Arabic and Roman notation, from I to MMMCMXCIX (1–3,999). The converter detects the input type automatically.
The converter detects the input type automatically
Quick examples
Arabic → Roman
What is Roman Numeral Converter?
Converts between Arabic numerals (1, 2, 3...) and Roman numerals (I, II, III...). Handy for checking centuries (XX, XXI), book chapters, clock faces, monarch names (Louis XIV) and inscriptions on monuments.
How to use
- Type a number in either field.
- The other side updates automatically.
- Supports numbers from 1 to 3999 (classic Roman limit).
- Invalid Roman letters are flagged.
Frequently asked questions
What is the largest number I can convert?
Standard Roman numerals only go up to 3,999 (MMMCMXCIX). Numbers above that historically used overlines, which we do not support.
Why is 4 written as IV and not IIII?
Modern subtractive notation uses IV for 4 and IX for 9. Older clocks sometimes still use IIII for stylistic reasons, but IV is the standard.
Does it accept lowercase Roman letters?
Yes — the converter normalizes input to uppercase, so iv and IV both work.