Cost per Thousand (known as CPM) is used in marketing as a benchmark to calculate the relative cost of an advertising campaign or an ad message in a given medium. Rather than an absolute cost, CPM estimates the cost per 1000 views of the ad.
It is calculated by:
total cost * 1000 / total audience
For example, while the Super Bowl has the highest per-spot ad cost in the United States, it also has the most television viewers annually. Consequently, its CPM may be comparable to a less expensive spot aired during standard programming.
The “M” in CPM derives from the Latin mille for “thousand.”
In the United Kingdom, Cost Per Thousand is expressed as CPT rather than CPM.