Roman Numeral Converter
Convert ordinary numbers into Roman numerals, or decode Roman numerals back into numbers. Works for 1 to 3999, the standard range, and runs entirely in your browser.
How Roman numerals work
Roman numerals build numbers from seven letters: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Letters are added together left to right, except when a smaller value sits before a larger one — then it’s subtracted. That’s why IV is 4 and IX is 9.
Why the 1–3999 limit?
Standard Roman numerals don’t have a symbol for zero and only go up to 3,999 (MMMCMXCIX) using the basic letters. Larger numbers historically used bars over letters to multiply them by 1,000, which most modern uses skip. This converter validates both directions, so a malformed numeral like IIII is flagged rather than silently misread.
Common uses
Roman numerals still appear on clock faces, book chapters, movie sequels, Super Bowl numbers, building cornerstones, and copyright years. This tool is handy for reading those off — or for writing a year like 2026 in numerals for a design.