CPM (cost per mille)

CPM stands for cost per mille: the price an advertiser pays for one thousand impressions (“mille” is Latin for thousand). It is the most common way to compare prices across media.

The formula is simple: CPM = (total cost ÷ impressions) × 1,000. If a campaign costs 500 and delivers 100,000 impressions, the CPM is 5.

In out-of-home, an impression is a contact: a person who had the opportunity to see the ad. One play on a busy screen can produce many contacts at once, which is different from online advertising where one impression usually equals one device. That is why CPM figures should always be read together with how the impressions were counted.