Roman Numeral Converter
Convert decimal numbers to Roman numerals and Roman numerals to decimal. Supports 1 to 3999 with full validation. Free online converter.
About this tool
Convert between decimal numbers and Roman numerals instantly. Type in either field and the other updates automatically. The tool validates Roman numerals against standard rules including subtractive notation (IV for 4, IX for 9, etc.).
Supports numbers from 1 to 3999, the standard range for Roman numeral representation. All processing happens in your browser.
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Frequently Asked Questions
What number range is supported?
The converter handles numbers from 1 to 3999. Roman numerals do not have a standard representation for zero or numbers above 3999.
How does validation work?
The tool checks for invalid Roman numeral patterns. For example, 'IIII' is invalid (should be 'IV'), and 'VV' is invalid (should be 'X').
What are the subtractive rules?
Smaller values before larger ones indicate subtraction: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900.