Roman Numeral Converter

Roman numerals write the seven letters I (1), V (5), X (10), L (50), C (100), D (500), and M (1000) from largest to smallest and add the values together. The same letter may be repeated at most three times, and V, L, and D are never repeated. They are still used on clock faces, for book chapter numbers, and for production years in film credits.

Instead of writing 4 as IIII, a smaller letter placed on the left means subtraction. Only six pairs are allowed: IV (4), IX (9), XL (40), XC (90), CD (400), and CM (900). Forms such as IC (intended as 99) or VX are not valid. 1994 is M + CM + XC + IV, which gives MCMXCIV.

Numbers of 0 or below, 4000 or above, decimals, and Roman numerals that deviate from standard notation such as IIII, VX, or MCMC are reported as errors. Both uppercase and lowercase letters are accepted for reading, and the result is shown in uppercase.

Standard Roman numerals use the seven letters I, V, X, L, C, D, and M, and the same letter may be repeated at most three times. Three of the largest letter M (1000) as MMM plus CM (900), XC (90), and IX (9) gives 3999 (MMMCMXCIX), the largest value standard notation can express. There is also no letter for zero.

Placing a smaller letter to the left of a larger one means subtraction. Only six pairs are used: IV=4, IX=9, XL=40, XC=90, CD=400, and CM=900. Writing the same letter four times, as in IIII, is not valid in standard notation. This tool converts using subtractive notation and reports malformed numerals as errors.

No. The conversion runs entirely in JavaScript within your browser. The numbers and Roman numerals you enter are never sent to or stored on any server.