Combination & Permutation Calculator

Quickly calculate C(n,r) combinations or P(n,r) permutations with step-by-step factorial work. A combination counts how many ways you can choose r items from n when order does not matter — like picking a committee from a group. A permutation counts arrangements where order matters — like awarding 1st, 2nd, and 3rd place. Toggle between modes, enter n (total items) and r (items chosen), and the calculator expands the factorial formula so you can see exactly how the answer is computed. Handles values of n up to 170.