What is CPM (Cost Per Mille)?

CPM (Cost Per Mille) is the price of one thousand ad impressions. It is the default billing model in display, video, native, and some social campaigns where billing is impression-based, not click-based.

Formula

CPM = (Ad spend ÷ Impressions) × 1000. Related: CPC ≈ CPM ÷ (CTR × 1000) when CTR is a decimal (1% = 0.01).

When it is used

Brand/reach, video views, push/native networks on CPM rates. Performance buyers translate CPM to expected CPC and compare to EPC. Low CPM with zero CTR delivers no landing traffic.

CPM vs eCPM

eCPM (effective CPM) recalculates per thousand impressions using actual revenue or full funnel cost. Publisher eCPM is earnings; buyer eCPM is cost-side.

Notes

Viewable CPM (vCPM) counts only viewable impressions. Bot impressions inflate the denominator. GEO and placement heavily change CPM—US tier-1 vs tier-3.

See also: CPC, CTR, impression, display ads.