Roman Numeral Converter
Convert between decimal numbers and Roman numerals instantly. Supports 1–3999 with full validation.
What Is Roman Numeral Converter?
Roman Numeral Converter translates between standard decimal integers and Roman numerals. Enter a number (1–3999) to get the Roman numeral, or type a Roman numeral to get the decimal value. Conversion is instant and bidirectional.
How to Use
- Type a decimal number (1–3999) in the left field to convert to Roman numerals
- Type a Roman numeral in the right field to convert to decimal
- Click any example to load it instantly
Roman Numeral Reference
- I = 1, V = 5, X = 10, L = 50
- C = 100, D = 500, M = 1000
- Subtractive notation: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900
FAQ
Why is the range limited to 1–3999?
Standard Roman numerals use M for 1000, and three Ms (MMM) gives 3000. Numbers above 3999 require non-standard extensions (vinculum notation) not covered by this tool.
How is input validated?
Roman numeral input is validated by round-tripping: the parsed decimal is converted back to Roman and compared to the input. Invalid sequences (e.g. IIII, VV) are rejected.
Is zero a valid Roman numeral?
No. The Romans had no symbol for zero. The concept was introduced to Europe later via Arabic numerals.