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Roman Numeral Converter
Convert between Roman numerals and decimal numbers
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Results
Result
About Roman Numeral Converter
Convert decimal numbers to Roman numerals (1-3999) or Roman numerals back to decimal. Shows the breakdown of each numeral component.
How It Works
For decimal to Roman: decomposes the number into Roman numeral components (M=1000, CM=900, D=500, etc.) using subtractive notation. For Roman to decimal: parses each character pair, validates the result by round-tripping.
Step by Step
- 1 Select conversion direction: to Roman or to Decimal
- 2 Enter a number (1-3999) or a Roman numeral string
- 3 Click Convert to see the result and breakdown
Tips
- Valid Roman numerals use: I, V, X, L, C, D, M
- Subtractive notation: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900
- Maximum value is 3999 (MMMCMXCIX)
- The converter validates Roman numerals and warns about non-standard forms
Frequently Asked Questions
What is the largest Roman numeral?
Using standard notation, the largest number is 3999 (MMMCMXCIX). Numbers 4000 and above require a vinculum (overline) notation not commonly used.
Why is 4 written as IV instead of IIII?
Modern Roman numerals use subtractive notation: placing a smaller numeral before a larger one means subtraction. IV = 5 - 1 = 4. This is more compact than IIII.