Roman numerals still appear in film credits, clock faces, book chapters and monarch names. This free Roman numeral converter works both ways: turn ordinary numbers into Roman numerals, or decode Roman numerals back into digits — with validation so only proper numerals are accepted. Everything runs in your browser.
How to Use
- To convert to Roman numerals, enter a number from 1 to 3999 and select “To Roman”.
- To decode, enter a Roman numeral such as MMXXIV and select “To Number”.
- Invalid entries show a helpful message instead of a wrong answer.
Key Features
- Two-way conversion in one tool.
- Validates Roman numerals against proper subtractive notation.
- Instant results with no sign-up required.
- Runs entirely in your browser.
FAQs
Why only 1 to 3999?
Standard Roman numerals have no widely agreed symbols above 3999 (MMMCMXCIX), so the tool keeps to the classic range.
Why was my numeral rejected?
The validator requires correct subtractive notation — for example IV for 4, not IIII — and rejects unknown letters.
Are the results case sensitive?
No. Lowercase input is converted to uppercase automatically.