Weighted CPM Calculator
Add rows for each campaign, then we’ll compute the weighted average CPM from total cost and total impressions.
What is weighted CPM?
Weighted CPM is the correct way to combine CPM across multiple campaigns. It weights each campaign by its impressions, so bigger campaigns count more.
Another way to say it: weighted CPM is the CPM you would get if you merged all rows into one big campaign with total cost and total impressions.
Key Takeaways
Use weighted CPM when you combine channels or campaigns.
Use total cost and total impressions to compute it correctly.
If you need one number for a report, weighted CPM is usually the right choice.
Avoid simple averages unless each row has similar impression volume.
Weighted CPM is especially important when one row is small but has extreme CPM.
If you want to compare performance, pair weighted CPM with CTR and CPA for outcome context.
Weighted CPM formula
The easiest correct formula is based on totals:
Weighted CPM = (Total Cost / Total Impressions) × 1000This is equivalent to weighting each campaign’s CPM by its impressions. If you sum all costs and all impressions first, you get a single CPM that matches the true blended result.
Example
A few examples you can verify. Notice how the “big” row dominates the blended CPM.
| Input | Output | Note |
|---|---|---|
| Row 1: Cost $100, Impressions 10,000; Row 2: Cost $50, Impressions 5,000 | Weighted CPM $10.00 | Total cost $150, total impressions 15,000 → (150/15000)×1000 = 10 |
| Row 1: Cost $1,000, Impressions 200,000 (CPM $5); Row 2: Cost $50, Impressions 5,000 (CPM $10) | Weighted CPM $5.12 | Totals: cost $1,050, impressions 205,000 → (1050/205000)×1000 ≈ 5.12 |
| Row 1: Cost $500, Impressions 25,000 (CPM $20); Row 2: Cost $500, Impressions 100,000 (CPM $5) | Weighted CPM $8.00 | Totals: cost $1,000, impressions 125,000 → (1000/125000)×1000 = 8 |
How to Use
Step 1
Add a row for each campaign, channel, country, or segment you want to include in the blended CPM.
Step 2
Enter Cost and Impressions for each non-empty row. Keep the same time window across rows.
Step 3
If any row is incomplete, fix it first—one missing value can distort the blended result.
Step 4
The calculator sums totals and computes Weighted CPM instantly from totals.
Step 5
Use the blended CPM for reporting, then compare row-level CPM to identify which segments are expensive.
Step 6
When CPM differs across geos or formats, don’t average the CPMs—always blend by impressions.
Step 7
Pair weighted CPM with CTR and CPA so you don’t optimize for cheaper impressions that reduce outcomes.
Frequently Asked Questions
A simple average treats a 1,000‑impression campaign the same as a 1,000,000‑impression campaign. Weighted CPM uses impressions as weights, so larger campaigns count more.
You need Cost and Impressions for each campaign/channel row. The calculator uses totals to compute weighted CPM.
Yes. Weighted CPM computed from rows equals (Total Cost / Total Impressions) × 1000.
Only when each row has similar impression volume and you’re confident the weights are effectively equal. In real campaigns, volumes differ a lot, so a simple average often misleads. If you need one number for stakeholders, weighted CPM is the safer default.
If you split rows but keep the same total cost and total impressions, weighted CPM stays the same. That’s the point: it reflects the blended total. What changes is your ability to diagnose which segments are driving the number.
Yes. A high-CPM row with small volume might not move the blended CPM much, but it can still be strategically important (for example, a premium audience segment). Use weighted CPM for summary, then inspect row-level CPM for decisions.
For CPM specifically, impressions are the correct weight because CPM is defined per 1,000 impressions. If your goal is performance efficiency, use CPC/CPA and weight by clicks or conversions for those metrics—not for CPM.
Exactly the same way: enter each country as a row with its cost and impressions for the same time window, then compute the blended CPM from totals. Countries with more impressions will naturally have more influence on the result.