Permutation & Combination Calculator
Enter n (total items) and r (selected items) to compute both nPr and nCr.
Permutation vs Combination
Permutation nPr — order matters
nPr = n! / (n − r)! — Example: arranging 3 of 5 books: 5P3 = 60
Combination nCr — order does NOT matter
nCr = n! / (r! × (n − r)!) — Example: choosing 3 of 5 books: 5C3 = 10
Relationship
nPr = nCr × r! — Permutations are always ≥ combinations.
