Cost per mille (CPM)(CPM)

Cost per mille (CPM) is what you pay for one thousand ad impressions. Formula: CPM = (spend ÷ impressions) × 1,000. Use CPM when buying or comparing awareness inventory (display, video, some social reach buys) — not when your goal is clicks or conversions, where CPC or CPA is the better lens. A $12 CPM on one platform is not automatically “more expensive” than $8 elsewhere if viewability, audience quality, or placement differ.

Platforms report CPM in the ads manager UI; auction CPM and billed CPM can diverge when pacing, frequency caps, or learning phase apply.