To make Roman numerals, we use seven letters from the alphabet. The letters, which are always capitalized, are I, V, X, L,C,D, and M. The table below shows you the value for each of these numerals.
Roman numerals are arranged and combined in a specific order to represent numbers.
Numerals (their values) are added together when written in groups, so XX = 20 (because 10+10 = 20). However, you cannot put more than three of the same numerals together. In other words, you can write III for three, but you can't use IIII. Instead, four is indicated with IV.
If a letter with a smaller value is placed before a letter with a larger value, you subtract the smaller from the larger. Sound a little confusing? It's not really. Consider:
IX = 9 because you subtract 1 from 10.
This list should help you get the hang of it!