Definition
A publisher running three networks on the same slot receives money three ways: one pays per thousand impressions, one per click, one per conversion. To decide which deserves the slot, the publisher converts all three to what they paid per thousand impressions shown. That number is the eCPM. The "e" marks that it was computed after the fact from actual revenue rather than quoted in advance as a price.
Formula and a worked example
eCPM = total earnings ÷ impressions × 1,000A placement showed 800,000 push notifications in a week. Network A paid per click and the clicks added up to $96; Network B paid a CPM and billed $72 for the same volume on a different week. eCPM for A: $96 ÷ 800,000 × 1,000 = $0.12. eCPM for B: $0.09. The publisher gives A the priority and keeps B as the fallback when A has no matching campaign, which is what a publisher's ad server does automatically when it ranks demand by eCPM.
eCPM vs RPM vs CPM
| Metric | Denominator | Used by |
|---|---|---|
| CPM | 1,000 ad impressions, quoted in advance | Advertisers (price) |
| eCPM | 1,000 ad impressions, computed from revenue | Publishers and advertisers (comparison) |
| RPM | 1,000 page views, all ad slots together | Publishers (site yield) |
RPM is always lower than or equal to the eCPM of the best slot because it divides by page views rather than ad impressions and includes unfilled inventory.
What moves a publisher's eCPM
The GEO and device mix of the audience (tier-1 desktop pays more than tier-3 mobile for most formats), the format (one popunder per visitor per day earns more than a banner the visitor ignores), viewability and position for display, click-through rate for CPC formats, and the demand the network can bring to that audience. Testing formats side by side with eCPM as the yardstick is how publishers decide what to run.
Related terms
| Term | Relation | Where defined |
|---|---|---|
| CPM | The quoted price this metric mirrors | Term page |
| RPM | Per page view instead of per ad impression | Glossary entry |
| CPC | One of the inputs | Term page |
| Ad server | Ranks demand by eCPM | Term page |
FAQ
What is the difference between CPM and eCPM?
CPM is a price set before delivery; eCPM is a result computed after delivery from actual revenue, so it works for campaigns paid per click or per conversion too.
Is a higher eCPM always better for a publisher?
Per impression, yes. But a network with a higher eCPM and a lower fill rate may earn less overall; compare total earnings per placement as well.
How can a publisher raise eCPM?
Run the formats that fit the audience, place display units where they are seen, keep page speed high so impressions count, and let the ad server rank networks by eCPM.