What Is CPM? A Practical Guide for Advertisers
Learn what cost per mille means, how to calculate it, and when CPM is the right advertising metric.
CPM explained
CPM stands for cost per mille, or the cost of one thousand advertising impressions. An impression is counted each time an advertisement is displayed. CPM gives advertisers a consistent way to compare the delivery cost of campaigns across publishers, formats, and platforms.
The CPM formula
To calculate CPM, divide the total campaign cost by the total number of impressions, then multiply by 1,000:
CPM = (total cost ÷ impressions) × 1,000
For example, a campaign that costs £500 and delivers 100,000 impressions has a £5 CPM.
When CPM is useful
CPM is most useful when reach and brand visibility are the primary objectives. It should be reviewed with engagement, conversion, audience quality, and revenue metrics when evaluating overall performance.