Roman Numeral Converter
Roman numeral converter: turn 1–3999 into Roman numerals and read numerals like MCMXCIV back to numbers, one per line, with strict checks. Free in your browser.
How to use Roman Numeral Converter
- 1Enter numbers or Roman numerals, one per line.
- 2Leave direction on Auto or force Number to Roman or Roman to Number.
- 3Copy the results; any line that is not valid is explained below the result.
What makes it better
- Automatic direction detection, line by line
- Strict validation of subtractive rules (IV, IX, XL, XC, CD, CM)
- Case-insensitive: xlii and XLII are the same
- Optional acceptance of additive forms such as IIII
- Built-in reference table of the seven symbols
About Roman Numeral Converter
The Roman Numeral Converter changes numbers from 1 to 3999 into Roman numerals and reads Roman numerals back into numbers. Direction is detected for every line, so you can paste a mixed list, and invalid forms such as IC or VX are rejected with a clear explanation.
Common uses
- Write years, chapter numbers or copyright dates in Roman numerals.
- Decode the date on a monument, clock face or film credit.
- Check homework or a document for correctly formed numerals.
- Convert a whole list of outline numbers at once.
Example
Input
2024 MCMXCIV 14 xlii
Result
MMXXIV 1994 XIV 42
Good to know
- The valid range is 1 to 3999. Roman numerals have no zero, and the overline (vinculum) notation for larger values is not supported.
- By default only standard forms are accepted: IIII is rejected unless you turn on additive forms, which also permit VIIII, XXXX and CCCC.
- In Auto mode a line made only of digits is converted to Roman; anything else is read as a Roman numeral.
Roman Numeral Converter FAQ
What is the largest number I can write in Roman numerals?
In the standard system it is 3999 (MMMCMXCIX), because M can repeat only three times. Larger values need an overline notation, which this tool does not use.
Why is IIII rejected? Clocks use it.
Standard rules write four as IV. Clock faces use IIII by tradition. Turn on “Accept additive forms such as IIII” if you need to read numerals written that way.
Why are IC and VX invalid?
Only I, X and C may be placed before a larger letter, and only before the next two larger symbols. So 99 is XCIX, not IC, and 5 is V, not an invalid subtraction like VX.
How do I convert the year 1999 to Roman numerals?
Type 1999 and the result is MCMXCIX: M (1000) + CM (900) + XC (90) + IX (9).