Roman to Decimal Converter

Convert Roman numerals to decimal numbers. Free online Roman numeral to Arabic number converter.

The Roman to Decimal Converter transforms Roman numerals into regular decimal (Arabic) numbers. Enter any valid Roman numeral to see its decimal equivalent with a breakdown of each symbol's contribution. Perfect for interpreting dates on historical buildings, movie sequels, and classic documents.

Common use cases

  • Interpreting building cornerstone dates
  • Understanding Super Bowl numbers
  • Reading historical documents
  • Academic citation numbering
  • Clock face reading

How to use

  1. Enter the Roman numeral
  2. Click convert for decimal value
  3. View symbol-by-symbol breakdown
  4. See additive and subtractive parts
  5. Learn the conversion rules

FAQ

How do I read Roman numerals?

Add values left to right, but subtract when a smaller value precedes a larger (IV=4, IX=9, etc.).

What is MCMXCIX?

M(1000) + CM(900) + XC(90) + IX(9) = 1999.

How do I know if subtraction applies?

Only I before V or X, X before L or C, and C before D or M use subtraction.

Are lowercase Roman numerals valid?

Yes, our converter handles both uppercase (XIV) and lowercase (xiv) input.