Convert instantly between numbers and roman numerals with this handy conversion tool. Convert Roman numerals to numbers and convert numbers to Roman numerals. Use this Roman numeral converter to convert numbers from 1 to 99,999 into Roman numerals. Or input a Roman numeral to get its regular number value. Roman numerals are a number system developed in ancient Rome where letters represent numbers. The modern use of Roman numerals involves the letters I, V, X, L, C, D, and M.