Roman numeral converter
Convert Roman numerals to decimal integers and back. This tool supports the traditional range from 1 to 3,999 and checks that Roman input uses canonical notation.
Enter a decimal number or a Roman numeral.
Examples
- 2024 = MMXXIV.
- 1999 = MCMXCIX.
- The converter accepts lowercase input and displays Roman numerals in uppercase.
How the converter checks Roman numerals
The decimal-to-Roman conversion uses the standard subtractive forms IV, IX, XL, XC, CD and CM. For Roman-to-decimal input, the result is converted back to canonical Roman notation; this rejects nonstandard forms such as IIII for 4.
Range and limitations
- The supported range is 1–3,999; zero has no standard Roman numeral in this notation.
- Numbers above 3,999 require extended conventions such as an overline, which this converter does not implement.
- The tool converts numerals; it does not determine historical usage or interpret dates in a document.
Frequently asked questions
Is there a Roman numeral for zero?
There is no standard Roman numeral for zero in the notation supported here.
Can I type lowercase Roman numerals?
Yes. Input is case-insensitive and the displayed result uses uppercase symbols.
Why is the range limited to 3,999?
The converter uses the usual standard notation without extended overline forms, so it supports integers from 1 through 3,999.