CPM (cost per mille)

CPM is the cost of one thousand ad impressions: what you pay for the ad to be shown, regardless of clicks. "Mille" is Latin for thousand.

It is the base price of attention on a platform, and it moves with auction pressure: quarter four is more expensive than February, and audiences every advertiser wants cost more than niches. Comparing your CPM month to month tells you about the market as much as about your ads.

CPM against CPC (cost per click) is a buying choice: paying per impression is better when your creative clicks above the market's expectation, paying per click transfers the risk of a dull creative to the platform. Ad platforms price accordingly.

For organic-first teams, CPM has one more use: it prices what your organic reach would have cost, which is the least bad way to put a number on "earned" attention when someone upstairs asks for one.

Related terms: CTR (click-through rate) · Impressions · Social media ROI