Roman Numeral → Decimal
Convert a Roman numeral to its decimal integer value. Validates canonical form.
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About Roman Numeral → Decimal
Parses a Roman numeral string and returns its decimal value. The parser validates that the input is in canonical form — MCMXCIV is accepted (1994) but MDCCCCLXXXXIIII is rejected even though it numerically represents the same value, because that's not the standard notation.
When to use it
- Decoding Roman numeral years on monuments or movies
- Parsing chapter or section numbers in outlines
- Solving puzzles or trivia that use Roman numerals
How it works
Each Roman symbol contributes its value, with subtraction applied when a smaller symbol precedes a larger one (IV = 5−1 = 4). After parsing, the result is round-tripped back to Roman numeral form to validate that the input matches the canonical representation.
Examples
MCMXCIV
1994
iv
4 (case-insensitive)
Frequently asked questions
- Is parsing case-sensitive?
- No. The input is uppercased before parsing, so 'mcmxciv' and 'MCMXCIV' both parse to 1994.
- Why is MDCCCCLXXXXIIII rejected?
- It's not canonical. The standard form for 1994 is MCMXCIV using subtractive notation. The validator catches non-canonical inputs to flag potential errors.