What is CPM?
CPM (cost per mille) is what an ad costs for every 1,000 times it is shown. It is the price of being seen, set by the ad auction, and it moves with competition, audience size and season. It says nothing about whether anyone clicked or bought.
The formula
Leave one field empty and it is worked out from the other two. With all three filled, CPM is worked out from spend and impressions. Impressions count every time an ad is shown, including repeat showings to the same person.
Worked example
$1,500 bought 120,000 impressions, which is $12.50 for every thousand.
Using it on Meta ads
Read CPM beside CTR: the two together set your cost per click. A rising CPM with a steady CTR means each click costs more, and in the end each purchase does too, which the CPA calculator shows.
In Ads Manager, CPM is amount spent divided by impressions, times 1,000. Compare it over the same dates and placements, since Reels, Feed and Stories cost different amounts.
Questions
Cost per mille, mille being Latin for thousand. It is the price of 1,000 impressions, which makes ad costs comparable across campaigns of any size.
CPM is set by the ad auction. More advertisers bidding for the same people, a narrower audience, or busy seasons such as the weeks before the holidays can all raise it.
No. A cheap impression that nobody clicks can cost more per sale than a pricier one that sells. Read CPM beside click-through rate and cost per purchase.
