Enter values and select Calculate.
Calculated result
How to use this calculator
- Choose the conversion direction.
- Enter an integer from 1 through 3,999 or a Roman numeral.
- Lowercase Roman input is normalized to uppercase.
- Review both the canonical numeral and integer result.
Formula and method
Values are assembled from conventional symbols and subtractive pairs: IV, IX, XL, XC, CD, and CM. Reverse conversion must reproduce the same canonical numeral.
Worked example
2026 becomes MMXXVI. MCMXCIX converts back to 1999, while malformed forms such as IC and IIII are rejected.
Assumptions and limits
- The supported system is conventional modern Roman notation.
- Zero and negative values have no output in this traditional range.
- Extended overline notation beyond 3,999 is not implemented.
- The later medieval N convention for zero is not used.
Understanding the result
The result follows the displayed deterministic method. Exact-integer operations use BigInt where appropriate, and any controlled precision limit is stated before the related output can be interpreted.
Common mistakes
- Repeating I four times instead of using IV
- Subtracting I from C as IC
- Assuming every sequence of Roman letters is valid
- Expecting zero or values beyond 3,999
Roman numeral chart
| Number | Roman numeral |
|---|---|
| 1 | I |
| 4 | IV |
| 5 | V |
| 9 | IX |
| 10 | X |
| 40 | XL |
| 49 | XLIX |
| 50 | L |
| 90 | XC |
| 100 | C |
| 400 | CD |
| 500 | D |
| 900 | CM |
| 1,000 | M |
| 1,999 | MCMXCIX |
| 2,026 | MMXXVI |
| 3,999 | MMMCMXCIX |
Roman numeral symbols and values
I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1,000.
Roman numeral conversion rules
- Add symbols when a symbol is followed by one of equal or lower value, as in VIII = 5 + 1 + 1 + 1.
- Use the standard subtractive pairs IV, IX, XL, XC, CD, and CM.
- I, X, C, and M may repeat up to three times in conventional notation; V, L, and D do not repeat.
- Noncanonical forms such as IIII and invalid pairs such as IC are rejected.
Common Roman numeral conversions
2026 → MMXXVI, 1999 → MCMXCIX, and 49 → XLIX.
Methodology note
The calculator uses the arithmetic definitions shown on this page. It does not call an external calculator service, evaluate expressions, or infer unselected mathematical conventions.
This deterministic utility is a calculation aid. Confirm required notation, precision, and course or professional conventions separately.