Metrics
CPM (Cost Per Thousand Impressions)
CPM is the cost of one thousand ad impressions and is the standard pricing unit for display, video, and social advertising where the platform sells reach rather than clicks.
In practice
Meta, YouTube, Display, and Demand Gen inventory is priced by impression, even when you optimize for conversions. CPM tells you how expensive the audience is: a tight, high-value audience on Meta costs far more per thousand than broad targeting, and CPMs across the board rise in Q4 when every retailer is bidding.
CPM matters as a diagnostic in two ways. Rising CPM with stable click and conversion rates means you are paying more for the same people, usually because of competition or audience saturation. A very low CPM often means the platform is serving to low-quality placements or inventory, which is common in Display and in PMax when it drifts toward Display.
CPM is not a performance metric on its own. A high-CPM audience with a high conversion rate can beat a cheap one on cost per acquisition. Read it alongside frequency, CTR, and conversion rate to understand what the platform is doing with the budget.
Why it matters
It is the price of attention on impression-based platforms and the first clue when delivery quality changes.
RELATED TERMS
CPC (Cost Per Click)
Cost per click is the amount paid for a single click on an ad, reported as an average across a keyword, ad group, or campaign.
CPA (Cost Per Acquisition)
Cost per acquisition is total ad spend divided by the number of conversions, giving the average cost to produce one defined outcome such as a sale, lead, or sign-up.
Brand Safety
Brand safety is the set of controls that keep ads from appearing next to content, placements, or contexts that would damage the brand, including content exclusions, placement exclusions, and inventory type settings.
Written by Ilya Bulychev, Founder, Live PPC Ads. Part of the PPC Glossary.
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