CPM formulas
| To find | Formula | Example |
|---|---|---|
| CPM | Cost ÷ Impressions × 1,000 | $500 ÷ 100,000 × 1,000 = $5.00 |
| Total cost | CPM × Impressions ÷ 1,000 | $8 × 250,000 ÷ 1,000 = $2,000 |
| Impressions | Cost ÷ CPM × 1,000 | $1,000 ÷ $8 × 1,000 = 125,000 |
| CTR | Clicks ÷ Impressions | 900 ÷ 100,000 = 0.9% |
| Effective CPC | Cost ÷ Clicks, or CPM ÷ (CTR × 1,000) | $500 ÷ 900 = $0.56 |
| Cost per conversion (CPA) | Cost ÷ Conversions | $500 ÷ 18 = $27.78 |
| ROAS | Revenue ÷ Cost | $1,800 ÷ $500 = 3.6× |
| Break-even CPM | CPC × CTR × 1,000 | $0.80 × 0.9% × 1,000 = $7.20 |
What makes a good CPM?
There's no single good CPM: it varies by platform, audience, country, ad format and season, and it usually rises in the fourth quarter when retailers bid up inventory. Judge a CPM by what it produces. A higher CPM that reaches buyers can have a lower cost per conversion than a cheap CPM that reaches no one, so add your clicks and conversions above and compare campaigns on CPA and ROAS.
CPM or CPC: which is cheaper?
Divide the CPM by your CTR × 1,000 to get what each click really costs. At a $10 CPM and a 1% CTR, clicks cost $1.00. If a publisher offers CPC pricing below that, CPC is cheaper; above it, CPM is. Full explanation: CPM vs CPC. Selling ads rather than buying them? Use the eCPM calculator.
Questions
How do you calculate CPM?
CPM = total cost ÷ impressions × 1,000. A campaign that costs $500 for 100,000 impressions has a $5.00 CPM.
How many impressions will my budget buy?
Impressions = budget ÷ CPM × 1,000. A $1,000 budget at a $8 CPM buys 125,000 impressions.
What does CPM stand for?
Cost per mille: the cost of 1,000 ad impressions. Mille is Latin for thousand.
Is CPM or CPC cheaper?
It depends on your click-through rate. Your effective CPC on a CPM buy is CPM ÷ (CTR × 1,000). At a $10 CPM and 1% CTR, each click costs $1.00, so a CPC offer above $1.00 would be more expensive.
What's the difference between CPM and eCPM?
CPM is what an advertiser pays per 1,000 impressions. eCPM (effective CPM) is what a publisher earns per 1,000 impressions across all pricing models: earnings ÷ impressions × 1,000.
Last reviewed 27 September 2026.