What is CPM (cost per mille) and how do you calculate it?
What CPM means, the formula to calculate it, and how publishers use CPM, eCPM and RPM to price and measure their ad inventory.
Written by Samhub with the help of AI·Updated 13 Oct 2026·4 min readCPM (cost per mille) is the price of 1,000 ad impressions. “Mille” is Latin for thousand. An advertiser who pays a €4 CPM pays €4 for every 1,000 times the ad is shown.
How CPM works
CPM is the most common way to price display, video and native advertising. The advertiser pays for exposure, not for clicks or sales. That makes CPM easy to compare across sites, formats and campaigns.
For publishers, CPM is the price your inventory sells for. In programmatic auctions it changes with every impression. In direct deals it is agreed up front, often from your rate card.
How to calculate CPM
You only need two numbers: the cost of the campaign and the number of impressions it delivered.
CPM = cost ÷ impressions × 1,000
Example: €3,000 ÷ 1,200,000 × 1,000 = €2.50 CPM
Impressions from a budget: €3,000 ÷ €2.50 × 1,000 = 1,200,000
Illustrative numbers. The same formula works in any currency.
CPM vs eCPM vs RPM
Three metrics look alike but answer different questions. CPM is the price per 1,000 impressions. eCPM is what you actually earned per 1,000 impressions across all pricing models. RPM is what you earned per 1,000 page views.
| What it measures | Who uses it | |
|---|---|---|
| CPM | The price per 1,000 impressions | Buyers and sellers, to agree on price |
| eCPM | Actual revenue per 1,000 impressions, whatever the pricing model | Publishers, to compare demand sources |
| RPM | Revenue per 1,000 page views | Publishers, to see what a page or site earns |
16 pages for publishers, with a checklist for data, programmatic and direct sales.
What affects your CPM
Audience
Impressions that reach a defined audience sell for more than impressions buyers know nothing about.
Format and placement
Large, viewable formats high on the page earn more than small units at the bottom.
Season
Demand peaks before holidays and in the fourth quarter, and drops in January.
How you sell
Direct deals and private marketplaces usually reach higher CPMs than the open auction.
How publishers raise their CPM
The surest way is to make your audience visible to the buyer. When impressions carry first-party audience data, buyers who need that audience bid more, and you can set higher floors in data deals.
CPM uplift at Stampen Media after activating first-party audiences with Samhub.
Frequently asked questions
Cost per mille. Mille is Latin for thousand, so CPM is the cost of 1,000 ad impressions. It is also called cost per thousand impressions.
It depends on the market, format, audience and season. Compare your CPMs over time and across your own placements, and against what buyers pay for the same audience elsewhere.
No. CPM is a price. eCPM is a result: what you actually earned per 1,000 impressions, which also includes campaigns sold per click or per action.
Divide the cost by the number of impressions and multiply by 1,000. €500 for 250,000 impressions is a €2.00 CPM.
Related terms
Effective revenue per 1,000 impressions.
What a publisher earns per 1,000 page views.
The lowest price a publisher accepts for an impression.
The share of ad requests that get an ad.
A fixed price per day for a placement.
Samhub audiences let you set higher floors and win more data deals, in every channel you sell.
- A walkthrough with your own data
- Built for publishers and media houses
- 30 minutes, no commitment
Turn your audience data into more revenue
Get the Media Monetization Playbook: how media houses turn first-party data into higher CPMs, data deals and direct sales. With checklists for every step.
