Calculates the number of combinations of n things taken r at a time. Find the number of combinations and/or permutations that result when you choose r elements from a set of n elements. For help in using the calculator, read the. Combinations and Permutations Calculator. Find out how many different ways you can choose items. For an in-depth explanation of the formulas please visit. Popular Calculators Derivative Calculator Inverse of Matrix Calculator Compound Interest Calculator Pregnancy Calculator Online. Enter a value in each of the unshaded text boxes. This calculator which generates possible combinations of m elements from the set of element with size n. To improve this 'Combination Calculator', please fill in questionnaire. We might ask how many ways we can space invasion game 2 letters from that set. Number of sample points in set n.