Permutation & Combination Calculator
Compute the number of permutations (nPr) and combinations (nCr) of r items from n.
Input Data
非負整數。
非負整數，r ≤ n。
Results
720
120
n=10, r=3
At a glance:nPr counts ordered selections of r from n; nCr counts unordered ones. Relation: nCr = nPr / r!.
Formula
nPr = n! / (n−r)!.
nCr = n! / (r!(n−r)!).
How to Use
- Enter n and r (r ≤ n).
- Read permutations and combinations.
FAQ
Permutation vs combination?
Permutations count order (AB ≠ BA); combinations treat them as the same group.
What if r > n?
You cannot choose r from n; the result is 0, and the tool will say so.
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References
Content review: Calculatorism Science Team. Results are for reference only.