Where CPM is used
Social platforms like Meta, TikTok and LinkedIn, display and video networks, and connected TV often price or report ads by CPM. Even when you're charged per click, CPM shows how expensive it is to reach an audience.
What drives CPM
How many advertisers want the same audience, how narrow your targeting is, the time of year, ad placement and how well your ad performs. CPMs often rise in the fourth quarter as retailers compete for holiday shoppers.
CPM vs CPC
CPM measures the cost of being seen. CPC measures the cost of a click. A high CPM can still give a low CPC if the ad gets clicked often, so look at both together, then at cost per acquisition.
Formula
CPM = (Total ad spend ÷ Total impressions) × 1,000
Use the same campaigns and date range for spend and impressions.
Why CPM matters
CPM tells you what it costs to reach people before anyone acts. Rising CPMs mean the same budget reaches fewer people, which pushes up every downstream cost unless your ads and pages convert better.
Cheap reach, expensive results
Campaign A reaches a broad audience at a $6 CPM. Campaign B targets a narrow, high-intent audience at an $18 CPM. B costs three times as much per impression, but its viewers click and buy far more often, so its cost per sale ends up lower.
Common mistakes
Chasing the lowest CPM
Cheap impressions often come from audiences or placements that rarely convert. Judge campaigns on cost per result.
Ignoring creative fatigue
As people see the same ad repeatedly, engagement drops and platforms can charge more to keep delivering it. Refresh creative regularly.
Comparing CPMs across platforms
A LinkedIn impression and a TikTok impression reach very different audiences. Compare within a platform, or compare final results.
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