When are Roman numerals used?Learn more about Roman numerals.(more)See all videos for this articleRoman numeral, any of the symbols used in a of based on the ancient Roman system. The symbols are I, V, X, , C, D, and , standing respectively for 1, 5, 10, 50, 100, 500, and 1,000 in the . A symbol placed after another of equal or greater value adds its value—e.g., II = 1 + 1 = 2 and LVIII = 50 + 5 + 1 + 1 + 1 = 58. Usually only three identical symbols can be used consecutively; to express numbers beginning with a 4 or a 9, a symbol is placed before one of greater value to subtract its value—e.g., IV = −1 + 5 = 4 and LIX = 50 -1 + 10 = 59. The exceptions are 4,000, which is sometimes written as MMMM, and clocks, which usually display 4 as IIII. A bar called a vinculum placed over a number multiplies its value by 1,000., List of Roman numerals / numbers., In the Roman numeral system, the symbols I, V, X, L, C, D, and M stand respectively for 1, 5, 10, 50, 100, 500, and 1,000 in the Hindu-Arabic numeral system. A symbol placed after another of equal or greater value adds its value. A symbol placed before one of greater value subtracts its value..