Convert numbers to Roman numerals and back.
Type a number (1–3999) to get its Roman numeral, or type a Roman numeral to get the number — both update automatically. Uses standard subtractive notation (IV, IX, XL, XC, CD, CM).
With standard notation the practical maximum is 3999 (MMMCMXCIX).
Letters I, V, X, L, C, D, M stand for 1, 5, 10, 50, 100, 500, 1000, combined additively and subtractively.