Roman Numeral Converter
Convert any number to Roman numerals or any Roman numeral back to a number, instantly.
MCMXCIV
How the Roman Numeral Converter works
Switch between the two modes to convert a number into a Roman numeral, or a Roman numeral back into a number. Numbers must be whole numbers from 1 to 3999, the standard range for subtractive Roman numeral notation.
The converter validates Roman numeral input by converting it to a number and back, so malformed numerals like “IIII” or “VV” are rejected rather than silently misread.
Frequently asked questions
What's the highest number Roman numerals can represent?
Using standard subtractive notation (like IV for 4 and IX for 9), Roman numerals top out at 3999 (MMMCMXCIX). Larger numbers require special notation (like a bar over a numeral to multiply it by 1000) that most modern tools, including this one, don't support.
Why is 4 written as IV instead of IIII?
Modern Roman numerals use subtractive notation: a smaller numeral placed before a larger one is subtracted rather than added. So IV means 5 minus 1 (4), and IX means 10 minus 1 (9). Older Roman inscriptions sometimes used IIII instead, but IV is the standard today.
Does the converter accept lowercase Roman numerals?
Yes — input like 'mcmxciv' is automatically converted to uppercase before being parsed, since Roman numerals are conventionally written in capital letters.