Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers instantly.
About this calculator
Two boxes, one for a number from 1 to 3,999 and one for a Roman numeral, and two buttons: To Roman and From Roman. The result shows the numeral and the number together, for example MMXXVI (2026).
A Clear button resets the form.
How to use it
- Type a number and press To Roman.
- Or type a numeral and press From Roman.
- Read the result line.
Rules
I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000. Subtractive pairs: IV, IX, XL, XC, CD, CM.
Worked example
Examples
| 2026 | MMXXVI |
| 1999 | MCMXCIX |
| XLII | 42 |
| MDCLXVI | 1666 |
Tips and common mistakes
- Check invalid forms: IC is not a valid 99; use XCIX.
- Enter numerals in capital letters.
- Use the numeral for dates on cornerstones.
- The largest standard value is 3,999.
- Clear before entering a new value.
Frequently asked questions
How do I convert a number to Roman numerals?
Break into thousands, hundreds, tens and ones and write each part.
What is 99 in Roman numerals?
XCIX.
What is 1666?
MDCLXVI.
What does MM mean?
2,000.
Is lowercase accepted?
Use capitals.
What about numbers above 3,999?
Standard Roman numerals cannot show them.