Combination Calculator
Math
Calculate combination with explicit inputs and a worked example.
Formula
C(n,k) = n!/[k!(n−k)!]
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Unordered selections without replacement; result uses exact integer arithmetic.
Example Calculation
Example inputs
- Available items n: 10
- Chosen items k: 3
Choosing 3 of 10 distinct items gives 120 combinations.
Frequently asked questions
How do I use this calculator?
Enter available items n, chosen items k. The result updates automatically. Use Reset to restore the example values.
What method does it use?
C(n,k) = n!/[k!(n−k)!]. Unordered selections without replacement; result uses exact integer arithmetic.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.