How to calculate CPM
CPM = (Ad cost ÷ Impressions) × 1,000
Worked example
A YouTube campaign promoting a new product line cost $1,200 and served 400,000 impressions.
CPM = ($1,200 ÷ 400,000) × 1,000 = $3.00
You paid $3 for every thousand times your ad appeared. You can also work backward: at a $3 CPM, a $600 budget buys about 200,000 impressions.
CPM vs CPC
CPM and CPC describe the same spending from different angles, connected by click-through rate:
Effective CPM = CPC × CTR × 1,000
If your Shopping campaign has a $0.30 CPC and a 1% CTR, its effective CPM is $0.30 × 0.01 × 1,000 = $3.00. The same $3 CPM can be cheap or expensive depending on what it produces:
| Campaign | CPM | CTR | Resulting CPC |
|---|
| A | $3.00 | 0.5% | $0.60 |
| B | $3.00 | 1.0% | $0.30 |
| C | $6.00 | 3.0% | $0.20 |
Campaign C has double the CPM but the cheapest clicks, because its ads are far more relevant to the people seeing them. This is why a low CPM on its own is never the goal. Pair it with the CTR calculator and the CPC calculator to see the full picture.
What is a good CPM?
CPM varies widely, so compare like with like rather than chasing an industry number. It depends on:
- Channel and placement. Display and video inventory is usually cheaper per impression than search results, where intent is higher.
- Audience targeting. Narrow, high-value audiences (recent site visitors, in-market shoppers) cost more to reach than broad audiences.
- Season. CPMs commonly rise in Q4, especially around Black Friday and Cyber Monday, when many advertisers compete for the same users.
- Competition in your category and the geographic markets you target.
- Ad quality and format. Engaging creative can earn more efficient delivery.
The most useful benchmark is your own history: track CPM by campaign and month, and investigate sudden jumps.
How to use CPM in your decisions
- Budget for awareness campaigns. If you know your typical CPM, you can estimate the reach a budget will buy before you launch.
- Spot rising competition. A CPM increase with no change in your targeting usually means more competitors in the auction.
- Judge creative. Compare CTR and conversion rate between ads at similar CPMs; the creative that converts better is worth more even if CPMs match.
- Do not optimize for CPM alone. The cheapest impressions often come from low-quality placements. For a store, cost per sale and profit matter far more than cost per view.
- Check placements in Performance Max. If a large share of impressions come from low-performing inventory, focus on stronger product data and audience signals rather than lowering CPM.