## How does it work?

CPM is shorthand for *cost per thousand* and is a common measure of volume in advertising. This calculator works either way, so it may be used to calculate either the cost, CPM or number of impressions. To calculate simply divide the cost by the number of impressions divided by a thousand. Below is the CPM formula and the reversed equations:

`CPM = 1000 * cost / impressions`

`cost = CPM * impressions / 1000`

`impressions = 1000 * cost / CPM`