Roman numeral converter
Convert between numbers 1 to 3999 and Roman numerals; 2026 is MMXXVI and XLII is 42.
- Runs in your browser
- No upload
- Instant result
Assumptions & formula
Formula and assumptions
I=1 V=5 X=10 L=50 C=100 D=500 M=1000; 1–3999
Results
Enter values and press Calculate to see the result here.
How to use this calculator
- Set inputs and units
Choose integer→Roman or Roman→integer. Enter a whole number or canonical Roman letters.
- Calculate
Check this worked example: 2026 → MMXXVI → 2026; 4 → IV
- Results
Check subtractive pairs such as IV and IX. The letter case of the input doesn't change the value.
Questions and limits
Why is IIII rejected?
The converter needs canonical subtractive notation: IV is 4. Some historical clock-face variants are deliberately not covered.
Which input errors should I correct?
Integers must be 1–3,999. Remove invalid letters, repeated groups that aren't allowed and non-canonical subtractive pairs.
What does this calculation leave out?
No zero, negative values, fractions, or overbar notation for values above 3,999.