Cost per Impression definition

A term used in internet marketing to refer to an advertising model where companies pay a specific amount of money each time an advert is displayed. One display of an advert to a user is known as an impression. Like other models, such as cost per click and cost per mille, cost per impression is used to establish the cost and ROI of online advertising campaigns. CPI is often used to compare the ROI of online advertising with traditional print mediums because impressions are similar to viewership or readership of a television or magazine advert.

The cost per impression is worked out by dividing the cost of the advertising campaign by the number of times the advert is shown. Because advertising campaigns often work across multiple websites with millions of page views per month, CPI is often expressed as cost per mille (CPM), or the cost to the advertiser for a thousand page impressions.