What is eCPM and how it differs from CPM, RPM, and CPC
eCPM (Effective CPM) normalizes any revenue source to a per-1,000-impression rate so demand sources can be ranked apples-to-apples.
eCPM = (Total Earnings ÷ Total Impressions) × 1,000
- vs CPM: CPM is what an advertiser bid. eCPM is what the demand source actually delivered after fill, viewability, and reconciliation.
- vs RPM: RPM is per pageview (publisher-side site total). eCPM is per impression (per ad-source slot).
- vs CPC: CPC is cost per click. eCPM converts CPC revenue into a CPM-equivalent so it ranks against impression-based demand.
How publishers and ad networks use eCPM to rank demand
Header bidding and waterfall stacks both rank demand sources by eCPM. Highest eCPM gets first look at each impression. The ranking changes every few minutes as the auction learns. Three implications:
- A demand source with low fill but high CPM (a luxury direct deal) can rank above AdSense if its average eCPM is higher.
- A demand source with 100% fill but low CPM (a remnant network) only wins when nothing else bids.
- The "best" demand partner isn't the one with the highest CPM — it's the one with the highest eCPM, accounting for fill rate and viewability.
For the publisher-side total see the RPM calculator; for the underlying CPM mechanics see CPM vs RPM.
Calculating eCPM from CPC and CPA (with worked examples)
For CPC-priced demand:
eCPM = CPC × CTR × 1,000
Example: $0.50 CPC × 1.2% CTR × 1,000 = $6 eCPM
For CPA-priced demand:
eCPM = CPA × CVR × CTR × 1,000
Example: $20 CPA × 5% CVR × 1.2% CTR × 1,000 = $12 eCPM
This conversion lets a header bidding stack rank a CPC display network against a CPM video network in the same auction.
When eCPM lies (low fill, viewability, ad density)
- Low fill rate. A demand partner with 30% fill but $20 CPM averages a $6 eCPM — and contributes only when nothing else bids.
- Low viewability. A header partner reporting $15 eCPM at 40% viewability is effectively a $6 eCPM partner once advertisers normalize.
- Ad-density confound. Doubling ad slots can double impressions but halve CPM, leaving eCPM identical. Don't credit the partner for the second slot.
eCPM benchmarks for header bidding partners
| Partner type | Typical eCPM (US tier-1) |
|---|---|
| Google AdSense / Ad Manager | $3 – $8 |
| Amazon TAM | $4 – $10 |
| Magnite (Rubicon) | $3 – $8 |
| PubMatic | $3 – $7 |
| Index Exchange | $4 – $9 |
| OpenX | $3 – $7 |
For an end-to-end revenue model see the ad revenue calculator.
Frequently asked questions about eCPM Calculator
What is eCPM and why does it exist?
eCPM converts CPC, CPA, or revenue-share earnings into a CPM-equivalent figure so different demand sources can be compared on the same basis.
How do I calculate eCPM from CPC?
Multiply CPC by CTR, then multiply by 1,000. The result is the effective CPM that demand source produces.
Why does eCPM matter for waterfalls and bidding?
eCPM is how header bidders and ad-server waterfalls rank demand. Higher eCPM wins the impression in real time.
Is eCPM the same as RPM?
Not quite. eCPM is per impression of a specific demand source. RPM averages all monetized and unmonetized impressions across pageviews.
How do I improve eCPM for a specific placement?
Test new creative formats, restrict low-value advertisers, and verify viewability scores before adding more demand to the waterfall.