Combinatorics Calculator

Calculate permutations (nPr), combinations (nCr), and factorials for counting problems.

Total number of items in the set. Must be a non-negative integer.
Number of items selected from the set. Must be ≤ n.

Results

n!
nPr — Permutations
nCr — Combinations
r!
(n-r)!

Formulas

n! = n × (n-1) × ... × 2 × 1
nPr = n! / (n-r)!
nCr = n! / [r! × (n-r)!]
References: Permutation: ordered arrangement of r items from n. Combination: unordered selection. Uses BigInt for arbitrary precision with large factorials.