Roman Numeral Rules

Everything you need to know about reading and writing Roman numerals.

The Seven Symbols

I

1

V

5

X

10

L

50

C

100

D

500

M

1000

Rule 1: Addition

When a symbol appears after a larger (or equal) symbol, add its value.

VI = 5 + 1 = 6

XV = 10 + 5 = 15

LXI = 50 + 10 + 1 = 61

MDCL = 1000 + 500 + 100 + 50 = 1650

Rule 2: Subtraction

When a symbol appears before a larger symbol, subtract its value. Only I, X, and C can be subtracted.

IV = 5 - 1 = 4

IX = 10 - 1 = 9

XL = 50 - 10 = 40

XC = 100 - 10 = 90

CD = 500 - 100 = 400

CM = 1000 - 100 = 900

Rule 3: Repetition

A symbol can be repeated up to 3 times. V, L, and D are never repeated.

III = 1 + 1 + 1 = 3 (correct)

XXX = 10 + 10 + 10 = 30 (correct)

IIII = invalid (use IV instead)

VV = invalid (use X instead)

Rule 4: Maximum Value

Standard Roman numerals can represent numbers from 1 to 3999. The largest number is MMMCMXCIX (3999).

Common Examples

Here are some commonly searched Roman numeral conversions: