CPM · cost per thousand impressions
CPM (cost per mille) is the price paid for one thousand displays of an ad, whether it gets clicked or not. It is the typical billing model for awareness campaigns.
The formula
CPM = (Total cost ÷ Number of impressions) × 1,000
A concrete example
Example
$300 for 150,000 impressions: CPM = (300 ÷ 150,000) × 1,000 = $2.
Why it matters
CPM mainly serves to compare the cost of visibility across ad platforms. For performance (leads, sales), you manage on CPC and cost per lead instead.