Roman Numerals

Updated June 26, 2019 | Infoplease Staff

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Roman numerals are expressed by letters of the alphabet and are rarely used today except for formality or variety. There are four basic principles for reading Roman numerals:

1. A letter repeated once or twice repeats its value that many times (XXX = 30, CC = 200, etc.).
2. One or more letters placed after another letter of greater value increases the greater value by the amount of the smaller (VI = 6, LXX = 70, MCC = 1200, etc.).
3. A letter placed before another letter of greater value decreases the greater value by the amount of the smaller (IV = 4, XC = 90, CM = 900, etc.). Several rules apply for subtraction: (a) only subtract powers of ten (I, X, or C, but not V or L); (b) only subtract one number from another; (c) do not subtract a number from one that is more than 10 times greater (that is, you can subtract 1 from 10 [IX] but not from 20—there is no such number as IXX).
4. A bar placed on top of a letter or string of letters increases the numeral's value by 1,000 times (XV = 15, = 15,000).

Letter	Value
I	1
II	2
III	3
IV	4
V	5
VI	6
VII	7
VIII	8
IX	9
X	10
XX	20
XXX	30
XL	40
L	50
LX	60
LXX	70
LXXX	80
XC	90
C	100
D	500
M	1,000
	5,000
	10,000
	50,000
	100,000
	500,000
	1,000,000