Roman Numeral Converter

Roman numerals still appear everywhere — on clock faces, in book chapters and movie sequels, on monuments, and in the names of monarchs and Super Bowls. Converting between them and ordinary numbers is a small but recurring need, and doing it by hand is easy to get wrong.

The seven symbols

Roman numerals are built from seven letters: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Numbers are formed by combining them, largest to smallest.

Subtractive notation

The tricky part is that Romans avoided four identical symbols in a row by using subtraction: 4 is IV (one before five), not IIII, and 9 is IX. The same applies to 40 (XL), 90 (XC), 400 (CD), and 900 (CM). This tool follows the standard subtractive form and validates input, so malformed numerals like "IIII" or "VX" are rejected rather than silently misread.

The 1–3999 limit

Classic Roman numerals have no symbol for zero and no standard way to write numbers above 3999 (that needs an overline to multiply by 1000). So this converter works within the well-defined 1–3999 range.

Type a number to get its Roman form, or a Roman numeral to decode it — everything runs in your browser.