Effective cost per mille (eCPM)
Effective cost per mille (eCPM) expresses earnings as revenue per thousand impressions, regardless of how the inventory was actually priced. It lets a publisher compare a CPC deal, a CPA deal, and a CPM deal on one common scale by back-calculating what each earned per thousand impressions. eCPM is a normalization metric — it measures yield, not the contract terms — and it depends on the same impression definition issues as CPM.
What this means
eCPM = (total earnings ÷ impressions) × 1000. Unlike CPM, which is a price the buyer pays, eCPM is a yield the publisher computes after the fact, normalizing any deal — pay-per-click, pay-per-action, or pay-per-impression — into revenue per thousand impressions so they can be compared.
Why publishers use it
A publisher running multiple monetization sources cannot directly compare a CPC network to a CPM network, because they price on different units. eCPM converts each to the same denominator: divide what the source earned by the impressions it consumed, times a thousand. The source with the higher eCPM yields more for the same inventory. Because the denominator is impressions, eCPM carries the same served-vs-viewable ambiguity as CPM — feed it consistent impression counts or the comparison breaks.
- eCPM = earnings per thousand impressions
- Normalizes CPC, CPA, and CPM sources onto one scale
- Yield metric for publishers, not a contract price
How it appears in analytics and logs
An eCPM figure tells you the revenue a source generated per thousand impressions. A higher eCPM means better yield for the same exposure, but it reflects the impression definition you fed in.
Diagnostic use case
Use eCPM to compare the yield of differently priced ad sources on a single per-thousand-impressions basis, especially when optimizing publisher inventory.
What WebmasterID can help detect
WebmasterID measures on-site engagement first-party, so publishers can read eCPM alongside what real visitors do rather than treating impressions as the only signal.
Common mistakes
- Confusing eCPM (publisher yield) with CPM (buyer price).
- Comparing eCPM across inconsistent impression definitions.
- Reading eCPM without the underlying impression volume.
Privacy and accuracy notes
eCPM is a revenue-per-thousand-impressions ratio; it is aggregate and needs no personal identifiers to compute.
Related pages
- Cost per mille (CPM)
Cost per mille (CPM) is the cost of one thousand impressions — 'mille' is Latin for thousand. It is the standard pricing unit for awareness and display buying, where advertisers pay for exposure rather than clicks. CPM depends entirely on how an impression is defined (served vs viewable), and it says nothing about whether anyone clicked or converted, so it is an exposure-cost metric only.
- Cost per click (CPC)
Cost per click (CPC) is the amount an advertiser pays for each click, calculated as total cost divided by clicks. In an auction-based system the actual CPC is set by competing bids and ad quality, not just your max bid. CPC measures the price of a click, not its worth — a cheap click that never converts is not a bargain — so it is read alongside conversion and value metrics, never alone.
- Viewability rate
Viewability rate is the percentage of measured ad impressions that qualified as viewable under an industry standard, rather than merely served. The IAB and MRC define a viewable display impression as at least 50% of the ad's pixels in view for at least one continuous second (two seconds for video). The rate exposes the gap between ads delivered and ads actually given a chance to be seen.
- Multi-site analytics
Compare yield signals across properties first-party.
Sources and verification notes
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.