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CPM is what you pay for 1,000 impressions: cost divided by impressions, times 1,000. Pick what you want to work out, fill in the other two, and the calculator also turns the CPM into a cost per click at your click-through rate. That second number is the one to compare across channels.
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CPM = cost / impressions x 1,000
Turn it around to plan a campaign. The cost of a reach goal is impressions / 1,000 x CPM. The impressions a budget buys are budget / CPM x 1,000. A $2,000 budget at a $12.50 CPM buys 160,000 impressions.
These are effective CPMs: what each campaign type cost per 1,000 impressions, whatever the bid strategy. Search is high because every Search impression is someone typing what they want, and advertisers bid more to be there.
| Campaign type | Median CPM | Middle half |
|---|---|---|
| Search 53 accounts | $306 | $180 to $453 |
| Performance Max 31 accounts | $21.07 | $12.92 to $42.14 |
| Shopping 16 accounts | $17.68 | $10.53 to $23.74 |
| Demand Gen 11 accounts | $13.15 | $9.93 to $22.73 |
US accounts I can see through the Google Ads API that spent $1,000 or more on the campaign type and recorded a conversion, 30 May 2026 to 28 Aug 2026. The middle half is the 25th to the 75th percentile.
Divide a CPM by the click-through rate before you compare two channels. In the accounts above, Demand Gen had the cheaper median CPM, $13.15 against $21.07 on Performance Max. Its median CTR was also lower, 0.66% against 1.29%.
Put those medians through the formula and a $13.15 CPM at 0.66% is $1.99 a click, while $21.07 at 1.29% is $1.63 a click. The cheaper impression bought the dearer click.
Then go one step further and divide by the conversion rate. My CPA calculator does that, and the CTR calculator shows where your click-through rate sits against the same accounts. If you're testing ChatGPT ads on a CPM bid, my ChatGPT ads guide has the CPM to CPC table for the CTRs advertisers have reported.
Divide the cost by the number of impressions, then multiply by 1,000. $500 for 40,000 impressions is $500 / 40,000 x 1,000 = $12.50 CPM.
Cost per mille. Mille is Latin for thousand, so CPM is the cost of 1,000 ad impressions. It is the standard price unit for display, video and social ads.
It depends on the channel. In the Google Ads accounts I can see, the median CPM was $21.07 on Performance Max and $13.15 on Demand Gen. A low CPM is only good if people click. Turn it into a cost per click before you compare channels.
Divide the CPM by 1,000 times your click-through rate. A $20 CPM at a 1% CTR is $20 / (1,000 x 0.01) = $2.00 a click. At a 0.5% CTR the same CPM costs $4.00 a click.
CPM is the price you bid or pay per 1,000 impressions. eCPM, or effective CPM, is what you actually paid per 1,000 impressions on any bid type. A CPC campaign still has an eCPM: cost divided by impressions, times 1,000.
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