eCPM (Effective CPM)

Effective CPM (eCPM) is the apples-to-apples comparison metric in programmatic advertising. It's nominal CPM divided by the impression quality rate — typically viewability rate × brand-safety pass rate × non-fraud rate. A $30 CPM with 70% viewability, 95% brand-safety pass, and 98% non-fraud has an effective CPM of $30 / (0.70 × 0.95 × 0.98) = ~$46.

eCPM lets a buyer rank inventory across formats. A $50 CTV CPM with 95% viewability has a lower eCPM than a $20 DOOH CPM with 100% viewability (sensor-counted) — assuming both are equally brand-safe and fraud-free. Without eCPM, buyers default to nominal CPM and systematically over-pay for low-viewability formats.

On the sell-side, "eCPM" also has a second meaning: the publisher's earned CPM after auction settlement. If a publisher sold 1M impressions for $25,000, its eCPM was $25.00. This sell-side eCPM is the headline yield metric in SSP dashboards.

For DOOH buyers comparing platforms, the sensor-counted audience advantage is what makes the eCPM math work in DOOH's favor. A Trillboards screen's nominal CPM may be $20 but its eCPM-against-attention-verified impressions is often lower than a $35-CPM CTV impression with modeled viewability — see attention metrics.