At One Place

Roman numerals

Roman numerals use seven symbols. Every number from 1 to 3,999 is built by adding them left to right, largest first, with six exceptions where a smaller symbol comes first and is subtracted instead.

The seven symbols

Symbol Value
I 1
V 5
X 10
L 50
C 100
D 500
M 1,000

The six subtractive pairs

No other subtractive combination is standard. IC and IIII are both wrong.
Pair Value Reads as
IV 4 V − I
IX 9 X − I
XL 40 L − X
XC 90 C − X
CD 400 D − C
CM 900 M − C

The system stops at 3,999 here because larger numbers need a vinculum — a bar drawn over a numeral to multiply it by a thousand — which has no settled plain-text form.

Commonly looked up

Common questions

Why is 4 written IV and not IIII?
Because standard notation never repeats a symbol four times. Placing I before V subtracts it, giving 4 in two characters instead of four. Clock faces are the well-known exception and often use IIII for visual balance.
Is there a Roman numeral for zero?
No. The system has no symbol for zero and no concept of it as a number — Roman numerals record quantities, and a quantity of nothing was simply not written.
What is the largest Roman numeral?
In standard plain notation, 3,999 — MMMCMXCIX. Beyond that a vinculum over a numeral multiplies it by a thousand, but that requires an overbar rather than ordinary letters.

Sources

  1. Calculated on this page — At One Place

How these figures are compiled and checked