ToolsJam

Roman Numeral Converter

Convert between Roman numerals and decimal numbers with this free online tool.

How to Use the Roman Numeral Converter

Decimal to Roman

  1. Select the "Decimal to Roman" tab
  2. Enter a decimal number between 1 and 3999
  3. Click "Convert" to see the equivalent Roman numeral
  4. Click the copy button to copy the result to your clipboard

Roman to Decimal

  1. Select the "Roman to Decimal" tab
  2. Enter a valid Roman numeral (e.g., MCMXCIV)
  3. Click "Convert" to see the equivalent decimal number
  4. Click the copy button to copy the result to your clipboard

Roman Numeral System

The Roman numeral system is an ancient number system that uses combinations of letters from the Latin alphabet to represent numbers. The basic symbols are:

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

Roman numerals are typically written from largest to smallest, from left to right. However, there are subtractive combinations where a smaller numeral before a larger one means subtraction (e.g., IV is 4, not 6).

Common Roman Numeral Examples

I
1
IV
4
V
5
IX
9
X
10
XL
40
L
50
C
100
D
500
M
1000
MCMXCIV
1994
MMXXIII
2023

FAQs

Why can't I convert numbers larger than 3999?

Traditional Roman numerals only go up to 3,999 (MMMCMXCIX). For larger numbers, additional notation is needed, which is not standardized.

Are Roman numerals still used today?

Yes, Roman numerals are still used in various contexts such as clock faces, book chapters, movie sequel numbering, and formal documents.

What are the rules for Roman numerals?

The basic rules are: numerals are usually written largest to smallest from left to right; when a smaller numeral appears before a larger one, it's subtracted (e.g., IV = 4); a numeral cannot be repeated more than three times in a row.