Roman Numeral Converter
Convert between Roman numerals and decimal
Calculator
How to Use
Convert between Roman and decimal numbers
Choose direction
Select Roman to decimal or vice versa
Enter number
Input Roman numeral or decimal number
View conversion
See the converted result
Learn notation
See breakdown of how the numeral works
Frequently Asked Questions
Roman numerals use letters: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Add values when smaller follows larger (VI=6). Subtract when smaller precedes larger (IV=4). Max standard is 3999 (MMMCMXCIX).
Only I, X, C can be subtracted, and only from the next two larger values. I before V or X (4=IV, 9=IX). X before L or C (40=XL, 90=XC). C before D or M (400=CD, 900=CM). Never subtract from a number more than 10× larger.
Subtractive notation (IV) is standard to keep numerals short. However, IIII appears on many clock faces (tradition from Roman times, visual balance). Both are technically valid, but IV is preferred in most contexts.
Standard Roman numerals go to 3999. For larger numbers, a bar over letters multiplies by 1000 (V̄ = 5000). In medieval times, various extensions existed. Modern use rarely needs numbers beyond standard range.
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