Roman Numeral Converter
Convert between Arabic numbers and Roman numerals with strict-mode validation, additive breakdowns, quick reference cards, and copy-friendly results.
Arabic → Roman
Primary
Standard Roman numerals are typically written for numbers from 1 to 3999. Disable strict mode to experiment beyond this range.
Roman → Arabic
Secondary
Use uppercase letters I, V, X, L, C, D, and M. Strict mode enforces the subtractive notation rules.
Strict mode
When enabled, restricts results to 1–3999 and enforces standard subtractive notation.
Roman numeral
XLII
Strict subtractive notation
Arabic value
42
Converted integer
Length
4 characters
Count of letters in the numeral
Additive form
XXXXII
Same value without subtractive notation
Building blocks
The numeral is composed of the following parts, listed in order.
XL = 40
I = 1
I = 1
Quick reference
Core numerals you can combine to express any number within the supported range.
I
1
One
V
5
Five
X
10
Ten
L
50
Fifty
C
100
One hundred
D
500
Five hundred
M
1000
One thousand