How to use this calculator
Combinations count selections where order does not matter.
The method
Enter your values in the labeled fields and choose Calculate. The result panel shows the answer and supporting values when useful.
Total items n: 10, Selected items r: 3
Select Calculate to evaluate these example values.
Scope and limitations
Requires 0 ≤ r ≤ n ≤ 1,000. Large results are shown approximately when they exceed exact integer precision. Uses real-number arithmetic and rounds display values without changing the entered inputs. Check important results independently.
Common questions
Can I use different units?
Use consistent units unless this page is a unit converter. The result follows the units implied by the inputs.
Are results exact?
Displayed values may be rounded. Keep extra precision for important follow-up calculations.
Methods & verification
Formulas use standard mathematical definitions and fixed unit factors where applicable. See our methodology for numerical conventions, rounding, privacy, and limitations.