CPM is the meter running behind almost every ad campaign. Understanding it — and being able to solve it in any direction — turns a media buy from guesswork into arithmetic you can plan around.
The formula, three ways
At its heart CPM is cost ÷ impressions × 1,000. But the same relationship answers three questions: what CPM am I paying, what will a reach goal cost, and how much reach will a budget buy? This calculator solves for whichever variable you leave open.
Why 'per thousand'
Impressions come in the millions, so a raw cost-per-impression is an unreadable string of decimals. Normalising to a thousand views gives a tidy, comparable number — which is why CPM, not cost-per-impression, is the standard unit across the ad industry.
CPM in context
A low CPM only matters if the impressions reach the right people and drive action. Read CPM alongside click-through rate, conversion rate and viewability — cheap reach that never converts is expensive in disguise. CPM tells you the price of attention, not its value.
Frequently asked questions
Divide the total campaign cost by the number of impressions, then multiply by 1,000. For example, $500 for 100,000 impressions is a $5 CPM.
Cost per mille — 'mille' is Latin for thousand — so CPM is the cost of one thousand ad impressions.
It depends heavily on platform, format and audience. Broad display can run a few dollars, while niche or premium video placements can be $20 or more. Compare like-for-like placements rather than chasing an absolute number.
CPM is what an advertiser pays per 1,000 impressions. eCPM (effective CPM) applies the same per-thousand math to a publisher's earnings, letting you compare revenue across ad units and pricing models.