Roman numeral converter

Roman numerals, both ways

Roman numerals are still all around us: on clock faces, in the names of kings and popes, in film copyright dates, on monuments, in chapter and volume numbers, and in the naming of sports events such as the Super Bowl. Writing them by hand is easy to get wrong, especially for the years, and reading a long one is not much better. This converter does both jobs instantly.

How Roman numerals are built

Seven letters carry the values: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1000. Numbers are written by adding the values from largest to smallest, so XVI is 10 + 5 + 1 = 16. When a smaller letter comes before a larger one, it is subtracted: IV is 4, IX is 9, XL is 40, XC is 90, CD is 400 and CM is 900. The tool shows the pieces the number is made of, so you can see why 1994 is MCMXCIV: M, CM, XC, IV.

The limits

The standard system covers 1 to 3999. There is no symbol for zero, and there is no simple way to write 4000 or more without a line drawn over the letters, which multiplies the value by a thousand. Numbers outside the range are rejected instead of returning something misleading.

Non-standard forms

Some old clocks write four as IIII rather than IV, and you can see other variants in old inscriptions. The tool accepts them, gives you the value, and points out the usual form, so you know whether what you have read is standard.

What it does not do

It does not convert numbers with fractions or the medieval extensions. It works entirely in your browser. To write a number in words instead, see the number to words converter.