Roman Numeral Validator
Validate Roman numerals instantly with our free online tool. Check if numerals like XVIII, IC, or MCMXC are correct, get their decimal values, and learn proper Roman numeral rules. Perfect for students, teachers, and anyone working with Roman numbers.
Roman numerals use I, V, X, L, C, D, and M. No letter should repeat more than 3 times in a row.
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What Is a Roman Numeral Validator?
A Roman Numeral Validator checks whether a Roman numeral follows traditional Roman numbering rules. It helps you identify invalid sequences and shows the correct version instantly.
Common mistakes detected:
- Using "IC" instead of "XCIX"
- Writing "IIII" instead of "IV"
- Mixing lowercase and uppercase letters
How to Use the Validator
- Enter your Roman numeral in the box.
- Click Validate.
- The tool will show whether it's valid and its decimal value.
- If invalid, it will show the correct form.
Examples
| Input | Result | Correction |
|---|---|---|
| XII | ✅ Valid | — |
| IC | ❌ Invalid | XCIX |
| VX | ❌ Invalid | V |
| MCMXC | ✅ Valid | — |
Roman Numeral Rules Summary
Symbols: I, V, X, L, C, D, M
Subtractive combinations allowed: IV, IX, XL, XC, CD, CM
No repetition more than 3 times in a row
Larger symbols come before smaller ones, except in subtractive cases
Frequently Asked Questions
Last updated: 01/18/2025