Roman Numeral Converter: How Roman Numbers Work

Roman numerals show up on clocks, movie credits, book chapters and monuments — and reading them trips people up. Here's how Roman numbers work, and how to convert them instantly.

Convert numbers to Roman numerals

Enter any number (1–3999) into the Roman numeral converter to get its Roman form, or paste a Roman numeral to decode it back to a normal number.

The seven symbols

I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000. Every Roman numeral is built from these seven letters, largest to smallest, added together — so MMXXVI is 1000 + 1000 + 10 + 10 + 5 + 1 = 2026.

The subtraction rule

To avoid four repeated symbols, a smaller symbol before a larger one means subtract: IV = 4 (5−1), IX = 9, XL = 40, CM = 900. That's why clocks show IX for 9, not VIIII.

Why 3999 is the limit

Standard Roman numerals only go up to 3999 (MMMCMXCIX) because there's no single symbol for 5000 or 10000 — beyond that needs overlines, which the everyday system doesn't use.

Common uses

Reading copyright years in film credits, Super Bowl numbers, book volumes, clock faces and outline numbering. A quick convert saves squinting at MCMLXXXIV (1984).