Cost per mille (CPM) is the cost of showing an ad one thousand times. “Mille” is Latin for thousand. Some campaigns are billed on CPM, and every platform reports it, which makes it a common way to compare how expensive it is to reach an audience on different channels.
The formula
CPM normalizes cost to a thousand impressions so you can compare campaigns of different sizes.
CPM = (Total cost / Impressions) x 1,000
Example: ($450 / 30,000) x 1,000 = $15When CPM is the right lens
On paid social and video, the platform often charges per impression, or optimizes toward an outcome while still pricing delivery by impression. Here CPM tells you what it costs to reach your audience, and click-through rate and conversion rate tell you whether that reach is working.
Narrow B2B audiences, such as a job title at companies of a certain size, usually carry higher CPMs than broad consumer audiences. That is expected: you are paying for precision.
Variants you will see
- vCPM: cost per thousand viewable impressions, where the ad met a viewability standard.
- eCPM: effective CPM, used to compare campaigns bought on other models by converting their cost to a per-thousand basis.
- Target CPM: a bidding strategy on some platforms for awareness campaigns.
Example
Comparing two audiences
Hypothetical company Hollowfern tests LinkedIn ads to finance directors and to a broader group of finance staff. The directors’ audience has the higher CPM, but more of those impressions turn into demo requests, so the cost per demo is lower. The team keeps the narrow audience despite the price per thousand.
Common mistakes
Picking the cheapest CPM
Low CPMs often mean a broad or low-value audience. The outcome per dollar matters more than the reach per dollar.
Questions
There is no universal figure. CPMs vary widely by platform, audience, country, season and creative. Compare against your own history and against the outcome you are paying for.
