CPM, eCPM and RPM explained for buyers and publishers

24 October 2026, 2 min read

Ad reports are full of short terms that look alike. CPM, eCPM and RPM all talk about 1,000 of something, but each one answers a different question. In this entry you will learn what each term means, how to calculate it, and how to use it without being misled.

CPM: the price of 1,000 impressions

CPM stands for cost per mille. Mille is Latin for thousand. CPM is the price paid for 1,000 ad impressions. An impression is one time an ad is shown.

The formula is cost divided by impressions, multiplied by 1,000. For example, imagine an advertiser spends 20 dollars and receives 10,000 impressions. The CPM is 2 dollars. Buyers use CPM to set bids and to compare placements. In OpenRTB, the open standard for real-time bidding, bid prices are also expressed as CPM.

eCPM: one yardstick for different pricing models

eCPM means effective CPM. Not every ad is sold per thousand impressions. Some are sold per click (CPC, cost per click) or per action (CPA, cost per action). eCPM converts the earnings of any model into an amount per 1,000 impressions, so you can compare them fairly.

The formula is total earnings divided by impressions, multiplied by 1,000. Imagine a click-priced ad pays 0.10 dollars per click, and 1,000 impressions bring 5 clicks. Earnings are 0.50 dollars, so the eCPM is 0.50 dollars. You can now compare it with a fixed-CPM ad paying, for example, 0.40 dollars.

• CPM is usually a price you agree or bid before delivery.
• eCPM is a result you calculate after delivery.

RPM: the publisher view of a page

RPM means revenue per mille. Publishers use it to show how much ad revenue they earn per 1,000 pageviews. Some reports use sessions instead of pageviews, so check the definition in your own tool. RPM counts all ad revenue on the page, not just one slot.

Here is a simple example. Imagine a page has three ad slots, and 1,000 pageviews bring 3 dollars. The RPM is 3 dollars. Those pageviews showed 3,000 ads, so the eCPM is 1 dollar. The money is the same. Only the denominator, the number you divide by, changes.

• CPM divides by impressions bought.
• eCPM divides by impressions shown.
• RPM divides by pageviews or sessions.

Reading these numbers with care

A higher number is not always better. A high eCPM can come with a low fill rate, which is the share of ad requests that return an ad. Fewer ads shown can mean less total revenue. More ads on a page can raise RPM, but they can also slow the page and annoy visitors, who may then leave.

For advertisers, a low CPM does not prove a good deal. Cheap impressions may be seen by few people or reach the wrong audience. Always read price together with results.

• Advertisers: compare CPM with outcomes such as clicks or sign-ups.
• Publishers: read eCPM together with fill rate and page speed.
• Everyone: confirm the currency and the denominator in each report.

Wrap-up

CPM is a price, eCPM is a result per impression, and RPM is a result per page. Next time you open a report, write down which number you divide by before you compare anything.

Prepared by the DIGIWEBS team with the help of AI writing tools. General information only, not legal, tax or financial advice. Images by DIGIWEBS Media.