Roman Numeral Converter
Convert a number from 1 to 3999 into Roman numerals, or a Roman numeral back into a number, with checking.
What is the Roman Numeral Converter?
The Roman Numeral Converter turns a number from 1 to 3999 into Roman numerals, or a Roman numeral into a number. It detects which one you typed and checks that Roman numerals are written correctly, so IIII or VX are rejected with a message. Useful for dates, chapter numbers, clocks, film credits and homework.
How to use it
- Type a number between 1 and 3999, or a Roman numeral such as MMXXVI.
- The tool detects which kind you entered.
- Read the converted value in the result box.
- Fix the entry if you see an invalid-numeral message.
Roman Numeral Converter — FAQ
Why does the tool stop at 3999?
Standard Roman numerals have no symbol for 5,000 or more, and repeating M more than three times is not accepted, so 3999 (MMMCMXCIX) is the largest value.
Why is IIII marked invalid?
In standard modern writing 4 is IV. Some clock faces use IIII, but the checker follows the usual subtractive rules.
Can I type lowercase Roman numerals?
Yes. mmxxvi and MMXXVI give the same answer, and spaces around the entry are ignored.