What is Cost per Mille (CPM)?

Cost per Mille, abbreviated CPM, is the price of one thousand ad impressions. It is the standard pricing unit in display, programmatic, video, and most upper-funnel awareness buys, where the goal is reach and frequency rather than immediate clicks or conversions.

Definition

CPM is calculated by dividing total media cost by impressions delivered and multiplying by one thousand. The metric isolates the cost of being seen, independent of user response, which makes it useful for comparing inventory quality across publishers, formats, and audiences. CPMs vary enormously - premium video on connected TV can clear at fifty euros or more, while remnant display inventory may sell below one euro. A meaningful CPM read also requires viewability and brand safety filters, because impressions that never enter the visible viewport inflate the denominator and distort efficiency.

Why it matters

In a composable commerce setup, CPM is the lever that determines how much of the audience funnel a brand can afford to fill before retargeting and conversion campaigns kick in. Headless storefronts that publish content across multiple channels - PWA, app, in-store screens - need consistent identity resolution to make CPM-based reach campaigns measurable downstream. When the first-party data layer and the consent mode setup are clean, programmatic buyers can shift CPM budget from open exchanges toward private deals with better signal, which directly improves the conversion economics of every later touchpoint.

Use cases

A premium beauty brand books CPM-priced connected-TV inventory to drive incremental reach in a new launch market and measures lift through incrementality testing rather than last-click attribution. A marketplace runs always-on display retargeting at a controlled CPM ceiling to keep cart abandoners exposed without overspending on already-engaged users. A B2B commerce vendor uses CPM-based LinkedIn campaigns against lookalike audiences of existing customers, accepting higher CPMs in exchange for a tightly defined account list.