cost per mille

Cost Per Mille

The cost to serve an ad 1,000 times. 'Mille' is Latin for thousand. The standard pricing unit for display, video, and social media advertising bought on a reach basis. The acronym CPM also exists as a stub entry; this entry provides full context.

When you'd see it: Brand awareness campaigns, programmatic display, connected TV, social video, and any campaign where reach — not clicks or conversions — is the primary objective. Media buyers negotiate CPM rates with publishers and platforms. YouTube, Meta, and programmatic platforms all price inventory in CPM terms.

Why it matters: CPM measures the cost of reach. Comparing CPM across channels helps you find the cheapest way to put your message in front of a given audience — a key input for brand-building where direct response isn't the immediate goal. CPM is also the denominator when calculating effective CPC from impression-based buys (effective CPC = CPM ÷ CTR × 10).

Common mistakes: Confusing low CPM with efficiency. A $1 CPM reaching irrelevant audiences wastes every dollar more efficiently than a $10 CPM reaching buyers. CPM is a cost metric, not a value metric — pair it with viewability rates, brand lift studies, or downstream conversion data to know if the reach is actually working.

Related CTR, CPC, impression, ROAS, paid media