CPM
What This Page Answers
CPM, or cost per thousand impressions, measures how much you pay for 1,000 ad impressions. CPM is a price of attention opportunity. It reflects competition, audience constraints, placement, seasonality, creative quality, and auction dynamics.
Formula
CPM = ad spend / impressions x 1000
Example:
$1,000 spend / 100,000 impressions x 1000 = $10 CPM
What CPM Tells You
CPM helps diagnose:
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Auction pressure
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Audience cost
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Placement cost
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Seasonality
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Retargeting saturation
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Creative quality issues
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Scaling limits
It does not tell you whether the campaign is profitable by itself.
High CPM Is Not Always Bad
A high CPM can be acceptable when:
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Audience quality is high.
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CTR is strong.
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CVR is strong.
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AOV or LTV is high.
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The placement is premium and converts well.
A low CPM can be bad when impressions are cheap because they are low quality.
CPM And Funnel Stage
Upper-funnel campaigns may buy broader, cheaper reach. Retargeting campaigns often have higher CPM because audiences are smaller and more valuable. Search does not usually optimize on CPM, but the same auction pressure shows up through CPC.
Diagnostic Checklist
If CPM rises:
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Check seasonality and competition.
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Check audience size and exclusions.
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Check frequency and saturation.
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Check placement mix.
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Check creative engagement and relevance.
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Check budget scaling speed.
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Check policy or quality issues.
Practical Rule
CPM is the cost of entering the auction. Profit depends on what happens after the impression.