Roman Numeral Converter
Turn a number into Roman numerals or read a Roman numeral back as a number — with proper validation across the classic 1–3999 range.
The seven symbols
How Roman numerals work
Seven letters combine to build every number from 1 to 3999. Symbols are written largest-first and added up — except for the six subtractive pairs, where a smaller symbol in front of a larger one is subtracted.
Number → Roman
Type any whole number from 1 to 3999 and see its Roman form built with the standard additive and subtractive rules (like IV for 4 and IX for 9).
Roman → Number
Type a numeral in any case. It's validated against strict formation rules — malformed strings like IIII or VX are flagged rather than silently misread.
Copy & use
Grab the result with the Copy button for titles, clock faces, outlines, movie credits or dates — nothing is ever saved or sent anywhere.
Rules and limits
The six subtractive pairs are the only places a smaller symbol precedes a larger one: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). Everywhere else, symbols are added left to right. A symbol can repeat at most three times in a row, which is why 4 is IV rather than IIII.
Standard Roman numerals have no symbol for zero and no way to write negatives or fractions, and the largest value expressible without overline notation is 3999 (MMMCMXCIX). This tool therefore accepts whole numbers from 1 to 3999 and only recognises strictly well-formed numerals when converting back.
Private by design. Every conversion happens right here in your browser with plain JavaScript. Nothing you type is ever uploaded or stored — we never see it.