Roman Numeral Converter
Convert numbers (1-3999) to standard Roman numerals and back, with validation against the subtractive notation rules. Perfect for chapters, events, and clock faces. Runs in your browser.
About Roman Numerals
Roman numerals use I (1), V (5), X (10), L (50), C (100), D (500), M (1000). Standard form supports 1 through 3999. For binary, octal, and hex conversion use theNumber Base Converter.
Secure & Private Client-Side
This tool runs entirely in your browser. No data is sent to any server, ensuring your information remains private and secure.
About Roman Numeral Converter
Convert numbers (1-3999) to standard Roman numerals and back, with validation against the subtractive notation rules. Perfect for chapters, events, and clock faces. Runs in your browser.
Frequently Asked Questions
Why is the limit 3999? expand_more
Standard Roman numerals use a maximum of three identical symbols in a row, so the largest representable number is MMMCMXCIX (3999). Larger numbers require a vinculum (overline) for thousands.
What are the subtractive rules? expand_more
I before V or X means subtract one (IV = 4, IX = 9). X before L or C subtracts ten (XL = 40, XC = 90). C before D or M subtracts one hundred (CD = 400, CM = 900).
Why does my input fail validation? expand_more
The tool rejects non-standard forms like IIII for 4 or VV for 10. Use the canonical subtractive forms (IV, IX, XL, XC, CD, CM).
Need binary or hex conversion? expand_more
Use the [Number Base Converter](/tools/number-base-converter/) for base 2, 8, 10, and 16 conversions.
Is my input uploaded? expand_more
No. Everything runs locally in your browser.
Common Use Cases
- Numbering: Format chapter, volume, or section numbers in print.
- Events: Decode Super Bowl, Olympics, or sequel numbering.
- Watches: Read and design Roman-numeral clock faces.
- Education: Practice converting Roman numerals for class.