Roman Numeral Converter

Convert an Arabic number to Roman numerals — and back.

Number → Roman

Misc

Arabic number (1-3999)

Enter a number.

Roman → Number

CalcCore

Roman numerals

Enter Roman numerals.

Random Number Generator Unit Converter

The Roman numeral system

The Roman numeral system uses letters to represent values:

I = 1
V = 5
X = 10
L = 50
C = 100
D = 500
M = 1000

Why regular numbers are called "Arabic numerals"

The term "Arabic numerals" refers to the familiar decimal number system (0, 1, 2, 3... 9) we use every day. The name is historical: this numeral system originated in India but reached Europe through Arab mathematicians around the 10th-12th centuries, which is how the name became established in European languages. The term is used purely to distinguish this system from Roman numerals — it has no connection to modern geography or politics.

Notation rules

Addition: when symbols go from larger to smaller, their values are added (VI = 5+1 = 6).
Subtraction: when a smaller symbol precedes a larger one, its value is subtracted (IV = 5-1 = 4, IX = 10-1 = 9).
Repetition limit: a symbol can't repeat more than three times in a row (IV is used instead of IIII).

Where Roman numerals are still used

Centuries: "the 21st century" written as XXI century.
Monarchs and popes: Louis XIV, John Paul II.
Clocks: traditional clock faces with Roman numerals.
Book and film chapters: numbering volumes, series installments (Rocky IV).
Olympic Games: sequential numbering (e.g., the XXXII Olympiad).

The standard system supports numbers from 1 to 3999. For larger numbers, a bar was historically placed over a symbol to multiply its value by 1000.

FAQ

What's the largest range of numbers you can write in Roman numerals?

The standard Roman numeral system supports numbers from 1 to 3999. Larger numbers require special notation with a bar over the symbol.

Why does a smaller numeral sometimes come before a larger one?

This is the subtraction rule: when a smaller symbol precedes a larger one, its value is subtracted (e.g., IV = 5-1 = 4).

Where are Roman numerals still used today?

Roman numerals are used for numbering centuries, book chapters, clock faces, monarch names (Louis XIV), and some official documents.