Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers, from 1 to 3999.
About this tool
Roman numerals persist on clock faces, movie credits, book chapters, monarch names, and Super Bowl titles, nearly two thousand years after Rome stopped needing them. The system uses seven letters (I, V, X, L, C, D, M) with a subtractive rule: a smaller value before a larger one is subtracted, so IV is 4 and CM is 900.
This converter works in both directions for the standard range of 1 to 3999, the largest value expressible without overline notation. Decoding validates strict classical form, so IIII and IC are rejected in favor of IV and XCIX, matching the convention used everywhere numerals appear formally.
Frequently asked questions
Why does the range stop at 3999?
Standard notation has no symbol above M (1000), and four repeated letters are not allowed, so 4000 would need the overline notation used in manuscripts, which plain text cannot represent.
Is IIII ever correct?
Clock faces traditionally use IIII for 4, purely as a design convention. In standard modern usage, 4 is written IV.