An ordered arrangement is called permutation (nPr). Permutation is done by the arrangement of all or part of set of objects, where the order of object is very important. Combination (nCr) is the selection of all or any particular object where the order is not important. It is an unordered collection of unique set of data. Enter the number of sample points in set 'n' and in set 'r' into the permutation and combinations calculator to calculate nPr and nCr.