Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers.
Standard Roman numerals run from I (1) to MMMCMXCIX (3999) using subtractive notation (IV = 4, IX = 9). Invalid forms like IIII or VV are rejected. Runs in your browser.
Convert a number to Roman numerals or a Roman numeral back to a number, both ways at once. Covers the standard range I (1) to MMMCMXCIX (3999) using correct subtractive notation (IV, IX, XL…), and rejects invalid forms like IIII or VV. Useful for dates, clock faces, names and movie/book numbering. Runs in your browser.
How to use the Roman Numeral Converter
- Type a number to see its Roman numeral.
- Or type a Roman numeral to decode it back to a number.
- Copy whichever result you need.
Frequently asked questions
What's the largest number in standard Roman numerals?
3999 (MMMCMXCIX). Numbers above that need overlines (vinculum) to multiply by 1,000, which isn't part of the basic notation this tool uses.
Why is 4 written IV and not IIII?
Standard Roman numerals use subtractive notation: a smaller symbol before a larger one means subtraction, so IV = 5 − 1 = 4. IIII is sometimes seen on clock faces but isn't the standard form.
Is there a year zero in Roman numerals?
No. Roman numerals have no symbol for zero, so the converter starts at 1.