Glossary /
CPM
Efficiency & cost
CPM
What you pay for a thousand ad impressions — the base auction price that sets the ceiling on everything downstream.
Attribution & Measurement
Unit Economics
Data Governance & Nomenclature
Creative & Delivery
Audiences & Targeting
Mobile & Privacy
CPM (Cost Per Mille) is the cost of one thousand ad impressions. "Mille" is Latin for thousand. A $5 CPM means you pay $5 each time your ad is shown 1,000 times.
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What is CPM?
CPM is the unit price of reach. It strips spend down to what it costs to put your ad in front of a thousand pairs of eyes, regardless of clicks or conversions. It's the foundational input behind CPC and CPA — everything downstream inherits the auction price set here. It matters because CPM is mostly driven by demand: more advertisers competing for the same audience pushes the auction price up. Rising CPMs are often the first sign a channel or audience is getting saturated, even before performance metrics move. Use CPM to track auction-level cost trends, compare the relative expense of audiences or placements, and diagnose whether a CPA spike is a delivery problem (rising CPM) or a conversion problem (falling conversion rate).
CPM formula
CPM = (Ad Spend ÷ Impressions) × 1,000
Ad Spend is what you paid over the period. Impressions is the number of times your ad was served. Divide spend by impressions to get cost per single impression, then multiply by 1,000 to express it per thousand — the standard unit for buying reach.
Worked example
A paid-social campaign over one week.
Ad Spend
$2,000
Impressions
400,000
CPM
$5.00
($2,000 ÷ 400,000) × 1,000 = $5.00
Each platform counts an “impression” differently (served vs. on-screen vs. viewable), so the same CPM is not the same exposure across channels.
CPM formula
CPM = (Ad Spend ÷ Impressions) × 1,000
Ad Spend is what you paid over the period. Impressions is the number of times your ad was served. Divide spend by impressions to get cost per single impression, then multiply by 1,000 to express it per thousand — the standard unit for buying reach.
Worked example
A paid-social campaign over one week.
Ad Spend
$2,000
Impressions
400,000
CPM
$5.00
($2,000 ÷ 400,000) × 1,000 = $5.00
Each platform counts an “impression” differently (served vs. on-screen vs. viewable), so the same CPM is not the same exposure across channels.
How CPM differs across ad platforms
Google Ads
On the Display and YouTube networks Google bills on impressions and reports CPM directly; viewable CPM (vCPM) only counts impressions that actually rendered on screen. On Search, CPM is a derived diagnostic, not a billing unit — Search runs on CPC, so a Search "CPM" is back-calculated from spend and impressions.
Meta
Meta counts an impression the first time an ad enters the screen, and CPM is its core auction-pricing signal across Feed, Stories, and Reels. Because placements vary wildly in cost, a single account-level CPM blends very different inventory — compare CPM by placement, not just by campaign.
TikTok
TikTok reports CPM on served impressions and, being a younger auction with shifting advertiser demand, tends to show more volatile CPMs than mature platforms. Definitions of a "viewable" video impression differ from static-feed platforms, so cross-platform CPM comparisons aren't strictly apples-to-apples.
Common CPM misconceptions
A lower CPM always means more efficient advertising.
Cheap impressions to the wrong audience waste money. A higher CPM on a high-intent, well-targeted audience often delivers a far better CPA and ROAS than cheap, untargeted reach.
An impression means the same thing on every platform.
Platforms define impressions differently — when an ad is served, when it enters the screen, or when it's viewable. So identical CPMs across platforms aren't measuring the same exposure.
Frequently Asked Questions
What is CPM in simple terms?
CPM is what you pay for a thousand times your ad is shown. A $5 CPM means every 1,000 impressions costs you $5.
How is CPM calculated?
Why does CPM differ across ad platforms?
How does Clarisights report on CPM?
Attribution & Measurement
Unit Economics
Data Governance & Nomenclature
Creative & Delivery
Audiences & Targeting
Mobile & Privacy
CPM (Cost Per Mille) is the cost of one thousand ad impressions. "Mille" is Latin for thousand. A $5 CPM means you pay $5 each time your ad is shown 1,000 times.
?
?
What is CPM?
CPM is the unit price of reach. It strips spend down to what it costs to put your ad in front of a thousand pairs of eyes, regardless of clicks or conversions. It's the foundational input behind CPC and CPA — everything downstream inherits the auction price set here. It matters because CPM is mostly driven by demand: more advertisers competing for the same audience pushes the auction price up. Rising CPMs are often the first sign a channel or audience is getting saturated, even before performance metrics move. Use CPM to track auction-level cost trends, compare the relative expense of audiences or placements, and diagnose whether a CPA spike is a delivery problem (rising CPM) or a conversion problem (falling conversion rate).
CPM formula
CPM = (Ad Spend ÷ Impressions) × 1,000
Ad Spend is what you paid over the period. Impressions is the number of times your ad was served. Divide spend by impressions to get cost per single impression, then multiply by 1,000 to express it per thousand — the standard unit for buying reach.
Worked example
A paid-social campaign over one week.
Ad Spend
$2,000
Impressions
400,000
CPM
$5.00
($2,000 ÷ 400,000) × 1,000 = $5.00
Each platform counts an “impression” differently (served vs. on-screen vs. viewable), so the same CPM is not the same exposure across channels.
How CPM differs across ad platforms
Google Ads
On the Display and YouTube networks Google bills on impressions and reports CPM directly; viewable CPM (vCPM) only counts impressions that actually rendered on screen. On Search, CPM is a derived diagnostic, not a billing unit — Search runs on CPC, so a Search "CPM" is back-calculated from spend and impressions.
Meta
Meta counts an impression the first time an ad enters the screen, and CPM is its core auction-pricing signal across Feed, Stories, and Reels. Because placements vary wildly in cost, a single account-level CPM blends very different inventory — compare CPM by placement, not just by campaign.
TikTok
TikTok reports CPM on served impressions and, being a younger auction with shifting advertiser demand, tends to show more volatile CPMs than mature platforms. Definitions of a "viewable" video impression differ from static-feed platforms, so cross-platform CPM comparisons aren't strictly apples-to-apples.
Common CPM misconceptions
A lower CPM always means more efficient advertising.
Cheap impressions to the wrong audience waste money. A higher CPM on a high-intent, well-targeted audience often delivers a far better CPA and ROAS than cheap, untargeted reach.
An impression means the same thing on every platform.
Platforms define impressions differently — when an ad is served, when it enters the screen, or when it's viewable. So identical CPMs across platforms aren't measuring the same exposure.
Frequently Asked Questions
What is CPM in simple terms?
CPM is what you pay for a thousand times your ad is shown. A $5 CPM means every 1,000 impressions costs you $5.
How is CPM calculated?
Why does CPM differ across ad platforms?
How does Clarisights report on CPM?
See Viewable Impression across every channel in one report
See Viewable Impression across every channel in one report
See viewability and vCPM across every platform—display, video, programmatic— in one normalized report, instead of reconciling vendor numbers by hand.
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