What is a permutation?

A permutation is an ordered arrangement. nPr = n!/(n−r)! counts how many ways to pick r items from n in order. P(5, 2) = 20.

What is a combination?

A combination is an unordered selection. nCr = n!/(r!·(n−r)!) counts how many ways to pick r items from n without order. C(5, 2) = 10.

Using BigInt, so very large inputs (e.g. n = 1000) work without overflow. Results are displayed as full integers.

Both nPr and nCr are zero — you cannot choose more items than you have.

No — the math runs entirely in your browser.

Compute nPr and nCr — order matters, or it doesn't.

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Follow these steps — everything happens instantly in your browser.

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Step 1. Enter n (total number of items) and r (items chosen).
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Step 2. See nPr (permutations, order matters) and nCr (combinations, order doesn't) update instantly.
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Step 3. The factorial values of n, r and (n−r) are shown for context.

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