eCPM

eCPM, or effective cost per mille, is a metric used in digital advertising to measure estimated revenue earned per 1,000 ad impressions. It allows publishers to compare monetization performance across ad units, networks, demand sources, and formats.

Calculation: eCPM = (total revenue from ads / total impressions) × 1,000. Revenue includes payments from multiple demand sources and formats (display, video, native). Impressions are the number of times an ad is served or eligible to be served, regardless of whether it is actually viewed.

Relationship to CPM and CPC: CPM is the price advertisers pay per thousand impressions, while eCPM is the publisher's actual revenue per thousand impressions after auctions and fill rates. If the publisher uses different demand sources, eCPM can reflect the relative yield of each source.

Usage: Publishers monitor eCPM to optimize yield, compare ad networks and placements, and guide monetization decisions. Higher eCPM indicates more revenue per impression, but may be influenced by fill rate and competition.

Limitations and notes: eCPM is an average across a period and does not guarantee future earnings. It can be affected by seasonality, geography, user segments, ad blocking, and changes in ad formats. The term RPM is sometimes used interchangeably with eCPM, though RPM is often associated with revenue per thousand impressions seen by the publisher.