CPM is the cost per 1,000 ad impressions. Advertisers use CPM to compare the price of reach across platforms, placements, and audiences. The formula is ad spend divided by impressions, multiplied by 1,000.
This CPM calculator from 412 Freelancers solves for any of the three values. Enter spend and impressions to get your CPM. Enter spend and a target CPM to see how many impressions that budget buys. Enter impressions and CPM to estimate the spend required.
CPM prices attention, not outcomes. A low CPM with the wrong audience is still wasted budget, so read CPM next to click-through rate and cost per acquisition rather than on its own.