Glossary A–ZLetter C
CPM (cost per mille)
CPM is the price per thousand impressions: price divided by the number of impressions, times a thousand.
The abbreviation stands for “cost per mille”.
CPM makes advertising offers of different sizes comparable, for example a single screen with a whole network, or screens with posters and online advertising. Worked example: if a week costs 40 euros and 5,000 impressions are assumed, the CPM is 8 euros; the example is not a market figure. In programmatic trading, bids are often made as a CPM, which is then converted to individual plays.
The calculation is only as good as the number of impressions in the denominator. Two offers are therefore comparable only if both count the same impression level, such as people in the area or actual glances. A low CPM may simply rest on generously estimated impressions. Operators should disclose where their impression figure comes from, and advertisers should ask.