Roman Numeral Converter
Convert between Roman numerals and Arabic numbers with validation.
| Roman | Decimal | Rule |
|---|---|---|
| I | 1 | One |
| IV | 4 | Subtractive: 5 - 1 |
| V | 5 | Five |
| IX | 9 | Subtractive: 10 - 1 |
| X | 10 | Ten |
| XL | 40 | Subtractive: 50 - 10 |
| L | 50 | Fifty |
| XC | 90 | Subtractive: 100 - 10 |
| C | 100 | One hundred |
| CD | 400 | Subtractive: 500 - 100 |
| D | 500 | Five hundred |
| CM | 900 | Subtractive: 1000 - 100 |
| M | 1000 | One thousand |
Rule 1: Symbols are added left to right, largest to smallest (XVI = 16).
Rule 2: A smaller symbol before a larger one means subtraction (IV = 4, IX = 9).
Rule 3: Only I, X, and C can be subtracted. Maximum range: 1-3999.
How to Use Roman Numeral Converter
- 1
Enter a number
Type a decimal number or Roman numeral to convert.
- 2
See the conversion
View the result instantly as you type in either direction.
- 3
Copy the result
Click copy to grab the converted Roman numeral or number.
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