Roman Numeral Converter
Convert between Arabic numbers and Roman numerals (1–3999)
Roman Numeral
MMXXIV
Common Examples
About the Roman Numeral Converter
This Roman numeral converter turns numbers from 1 to 3999 into Roman numerals and converts numerals back to numbers, applying the subtractive notation rules correctly so 4 becomes IV rather than IIII.
A Roman numeral converter handles a system that looks simple and has awkward rules. Seven letters carry values — I, V, X, L, C, D and M — and are normally added together, so XVI is 16.
The subtractive rule is where hand conversion goes wrong. A smaller value before a larger one is subtracted, so 4 is IV and 9 is IX, and only certain pairs are permitted: I before V or X, X before L or C, and C before D or M. That is why 99 is XCIX and not IC.
The 3999 ceiling is real rather than arbitrary: M is the largest single letter, and standard notation allows at most three in a row, so MMMCMXCIX is the highest expressible value. Useful for dates on buildings, film credits, clock faces and outline numbering.
How to use the Roman Numeral Converter
- Pick a direction. Convert a number to numerals, or numerals to a number.
- Enter your value. Type a number from 1 to 3999, or a Roman numeral.
- Read the result. The conversion appears with correct subtractive notation.
- Copy it. Take the converted value.
Roman Numeral Converter features
- Numbers to Roman numerals from 1 to 3999
- Roman numerals back to numbers
- Correct subtractive notation such as IV and XC
- Validates malformed numerals
- Instant conversion as you type
- Runs entirely in your browser
Frequently asked questions
Why is 4 written IV rather than IIII?
Roman notation subtracts a smaller value placed before a larger one, so IV is 5 minus 1. Only specific pairs are allowed.
Why is the maximum 3999?
M is the largest single letter and at most three may appear in a row, making MMMCMXCIX the highest standard value.
Which subtractive pairs are valid?
I before V or X, X before L or C, and C before D or M. That is why 99 is XCIX and not IC.
Is there a zero in Roman numerals?
No. The system has no symbol for zero, which is one reason positional notation replaced it.
Can it validate a numeral I found?
Yes. Malformed numerals are reported rather than silently converted.