How to Convert Roman Numerals

By Education Editor

How to Convert Roman Numerals. You don't need to be in Rome to do everything the Romans do. Learn to convert Roman numerals like one of the natives.

How to Read Roman Numerals

Understand that the Roman numerals I, V, X, L, C, D and M represent the values 1, 5, 10, 50, 100, 500 and 1,000, respectively.

Add the two numerals together if a numeral is followed by one of equal or lower value. Thus, read II as "I + I," or "1 + 1," which equals 2; read VI as "V + I," or "5 + 1," which equals 6.

Subtract the first numeral from the second if a numeral is followed by one of a higher value. Thus, read IV as "1 less than 5," which is 4.

When reading larger numbers, distinguish the subtracted numbers (see step 3) before adding up the values. Example: DCXLIX = D + C + XL + IX = 500 + 100 + 40 + 9 = 649.

How to Write Roman Numerals

Break down the number into its basic components, beginning with the largest number. Example: 273 = 200 + 70 + 3.

Break down the numbers again, using your basic values (see step 1): (200) + (70) + (3) = (100 + 100) + (50 + 10 + 10) + (1 + 1 + 1).

Convert into the appropriate Roman numerals: (C + C) + (L + X + X) + (I+ I + I) = CCLXXIII). If you have more than 3 numbers in a row, keep the first numeral and subtract accordingly. Example: 400 = 100 + 100 + 100 + 100 = "100 less than 500" = CD, instead of CCCC.

Tip

One caveat to reading Roman numerals: Clocks and watches usually have IIII instead of IV for four.