Glossary
CPM: what it is and how to read cost per thousand impressions
Understand CPM, calculate the cost of a thousand ad impressions, and learn when a higher delivery cost matters for lead generation and sales.
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CPM means cost per thousand impressions. It measures the price of ad delivery, not the cost of a visitor or customer. For example, US$ 240 spent on 20,000 impressions produces a CPM of US$ 12. The same person may account for several impressions. A rising CPM tells you delivery became more expensive in that reporting mix; it does not explain whether the people reached became more valuable.
Formula
CPM = ad spend ÷ impressions × 1,000.
Match dates, currency and reporting scope. When combining campaigns, divide total spend by total impressions and multiply by one thousand. An unweighted average gives a tiny campaign the same influence as a large one.
With zero impressions there is no meaningful CPM to calculate. Display the underlying delivery status instead of a zero that looks like free media.
What makes a good number
A sustainable CPM depends on what the exposure produces. Imagine two hypothetical lead generation campaigns:
| Campaign | Spend | Impressions | Leads | CPM |
|---|---|---|---|---|
| A | US$ 300 | 30,000 | 10 | US$ 10 |
| B | US$ 300 | 15,000 | 20 | US$ 20 |
Campaign B has the more expensive exposure and the cheaper lead. Neither row proves profitability without qualification and sales data. The example shows why delivery cost should be a diagnostic metric rather than the final optimization target.
What changes the number
Audience, geography, placement, competition and time period influence delivery prices. The aggregate can also rise because spending shifted toward an expensive segment, even when each segment's own price stayed stable.
Check the distribution of spend before blaming auction competition. If CPM rises while click response and post-click conversion hold steady, media cost deserves attention. If CPM stays stable but leads drop, inspect the later stages. Keep CTR and CPL beside the delivery metric.
Choose a comparable baseline
Compare the same objective and a similar mix of placements and audiences. Annotate budget or targeting changes so the next review has context. A cheaper thousand impressions is useful only when it supports the job the campaign needs to do. See the paid media reporting workflow for bringing delivery and outcomes into one review.
Frequently asked questions
Does CPM count a thousand unique people?
No. It counts a thousand impressions, including repeat exposure to the same person.
Should I pause an ad because CPM increased?
Not on that metric alone. Review outcomes, quality and changes in the delivery mix first.
How do I combine CPM across campaigns?
Divide combined spend by combined impressions, then multiply by one thousand.