1. The problem statement, all variables and given/known data Is there a proof that the number of elements in a conjugacy class of a group has to divide the order of the group? Everyone seems to cite it left and right but I've not seen a proof of it anywhere. 2. Relevant equations 3. The attempt at a solution I'm guessing Langrange's Theorem may come into play but since conjugacy classes themselves aren't subgroups I'm not sure how.