eCPM

eCPM, or effective cost per mille, is the revenue earned or the cost paid per 1,000 impressions, worked out after the fact so that CPM, CPC and CPA campaigns can be compared on one scale.

Campaigns are priced in different ways. One buyer pays per thousand impressions, another per click, a third per sale. eCPM turns all of them into the same unit: total revenue or cost, divided by impressions, times 1,000. Publishers use it to compare demand partners and ad units. Buyers use it to compare the real cost of different buys.

Google's publisher products report the same calculation as RPM, revenue per thousand impressions: estimated earnings divided by impressions, multiplied by 1,000 (Google AdSense Help, accessed 9 November 2026).

An eCPM is only as good as its inputs. A high eCPM on low fill can earn less than a lower eCPM on high fill, so publishers multiply the two. Buyers should also check which impressions are counted. Measured, viewable and valid impressions give a truer price, which is what vCPM and quality-adjusted measures such as the ANA's TrueCPM try to capture.

Example: Google's own worked example: estimated earnings of $180 from 45,000 ad impressions give an RPM, or eCPM, of $4.00 (Google AdSense Help). A CPC campaign that paid $90 for 300 clicks on 30,000 impressions has an eCPM of $3.00.

Related terms: fill rate, vCPM, CPC, CPA, floor price, yield management.

Authoritative source: Google AdSense Help, "Revenue per thousand impressions (RPM)" (accessed 9 November 2026).