Convert between integers and Roman numerals — supports 1 to 3999 with validation.
Quick reference
The Roman Numeral Converter converts integers between 1 and 3999 to their Roman numeral equivalents, and validates Roman numeral strings back to integers. Invalid or non-canonical inputs (e.g. IIII instead of IV) are rejected with a clear error message.
Click any entry in the quick reference table to load it instantly. Use Swap to flip between integer and Roman modes without retyping.