CPM: Cost Per Thousand Impressions

Updated September 20, 2026· 7 min read

CPM (cost per mille) is what you pay for one thousand ad impressions. Compute it as media spend divided by impressions, times 1,000. Advertisers use it to compare the cost of delivery on paid media across Display, video, Connected TV (CTV), and social, including Facebook and Google buys.

CPM measures impression cost. Read it next to eCPM when evaluating publisher yield, and next to cost per click (CPC) when buying traffic. Use the CPM calculator to solve for CPM, spend, or impressions when you know the other two values.

Formula and algebra

CPM = (media cost / ad impressions) x 1,000
Spend = CPM x impressions / 1,000
Impressions = spend x 1,000 / CPM

Worked example, same arithmetic the calculator uses:

Known	Calculation	Result
Spend $500, 100,000 impressions	($500 / 100,000) x 1,000	$5.00 CPM
$5.00 CPM, $2,000 budget	$2,000 x 1,000 / $5.00	400,000 impressions
$5.00 CPM, 50,000 impressions	$5.00 x 50,000 / 1,000	$250 spend

Google Ads defines CPM as a way to bid where you pay per one thousand impressions on the Google Display Network. That is the buying model. Google Ads statistics columns also describe Avg. CPM as the average amount charged per 1,000 views of the ad (the Help text currently ties that column note to CPM bidding). On other buying models, teams still compute an effective CPM with the same spend / impressions x 1,000 arithmetic. Name which one you are looking at.

Auction delivery means the price of a thousand impressions is not a universally fixed rate card. Google’s target CPM (tCPM) for video sets an average you are willing to pay per thousand impressions. Some impressions can cost more or less than that target. Google says it tries to keep campaign average CPM at or below the target.

CPM versus viewable CPM, CPC, and CPA

Metric	What it measures	Denominator	Typical job
CPM	Media cost per 1,000 served impressions	Impressions	Compare the cost of delivery
Viewable CPM (vCPM)	Media cost per 1,000 viewable impressions	Viewable impressions	Compare the cost of viewable delivery
CPC	Media cost per click	Clicks	Compare the cost of traffic
CPA	Media cost per conversion	Account-defined conversions	Compare the cost of a named action

Google’s viewable CPM Help: you bid on 1,000 viewable impressions and pay for impressions measured as viewable. A display ad is viewable when 50% of it shows on screen for 1 second or longer. A video ad is viewable when it plays continuously for 2 seconds or longer (Google’s Active View Help also states the MRC 50% / 2 second video rule, with a 30% area rule for large display ads of 242,500 pixels or more). Max CPM is no longer available as a bid strategy on that Help page. vCPM is not offered for Search Network only campaigns. A small portion of served impressions might still be charged.

Avg. viewable CPM is cost per 1,000 viewable impressions. A $4 CPM and an $8 vCPM can describe the same campaign if half the impressions were not viewable. Do not compare them as if the denominator matched.

CPC and CPA change the denominator again. A $2 CPM is cheaper impression delivery than a $12 CPM, but the $12 CPM placement may create more valuable clicks or conversions. Before and after a targeting or creative change, calculate your CPM and read it beside the outcome the campaign is meant to produce.

What actually moves CPM

These are mechanisms, not a ranked playbook:

• Audience size and competition. Narrow or high-demand auctions often cost more per thousand.
• Format and inventory. In-stream video and premium placements often price higher than leftover display.
• Seasonality. Retail peaks can raise impression prices. That is calendar pressure, not a creative score.
• Viewability and measurability. Paying only for viewable impressions changes both the bid and the reported rate.
• Frequency. Repeating the same people can keep CPM looking stable while unique reach stalls.

A lower CPM can come from broader or less competitive inventory, while a higher CPM can come from scarce audiences, stronger viewability, or premium placements. Excluding low-quality placements may raise CPM and improve CPA; expanding inventory may lower CPM and reduce conversion quality. Set the campaign outcome before optimizing the delivery price.

IAB and PwC’s Internet Advertising Revenue Report for full year 2024, dated April 17, 2025, found US internet advertising revenue of $258.6 billion, up 14.9% year over year. The figure describes market size rather than an account-level CPM benchmark.

Use CPM to compare the price of delivery, then use viewability, clicks, qualified conversions, and conversion value to assess what that delivery produced.

CPM video explainer

Video: What are CPM, CPC, CPA & CTR? by Publift, published March 25, 2020.

Frequently Asked Questions

What is CPM in advertising?

CPM (cost per mille) is the cost of one thousand ad impressions. Compute it as spend divided by impressions, times 1,000. Platforms also use CPM as a bidding model, which is not the same thing as the reporting ratio.

How do you calculate CPM, spend, and impressions?

CPM = (spend / impressions) x 1,000. Spend = CPM x impressions / 1,000. Impressions = spend x 1,000 / CPM. Example: $500 spend and 100,000 impressions is a $5 CPM.

How is CPM different from viewable CPM, CPC, and CPA?

CPM uses impressions as the denominator. Viewable CPM uses impressions measured as viewable. CPC uses clicks. CPA uses conversions. Compare them only after you name those denominators. A cheaper thousand impressions can still produce a worse cost per conversion.

Is a lower CPM better?

Not by itself. A lower CPM can mean cheaper, less viewable, less relevant, or less competitive inventory. Read CPM next to reach quality, viewability, clicks, conversions, and conversion value.

Sources

• Google Ads Help, Cost-per-thousand impressions (CPM): Definition, accessed September 20, 2026.
• Google Ads Help, About columns in your statistics table, accessed September 20, 2026.
• Google Ads Help, Bid on viewable impressions using viewable CPM, accessed September 20, 2026.
• Google Ads Help, Target cost-per-thousand impressions (tCPM): Definition, accessed September 20, 2026.
• Google Ads Help, Active View, accessed September 20, 2026.
• IAB, Digital Ad Revenue Surges 15% YoY in 2024, dated April 17, 2025, accessed September 20, 2026.