Previously, we explained the differences between eCPM and CPM. This article will extend our discussion by comparing eCPM, rCPM, and fill rate. You’ll learn how these metrics differ, how they’re calculated, as well as which one to look at when assessing your monetization performance.
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But first, let’s refresh our knowledge about eCPM.
What is eCPM?
eCPM stands for effective cost-per-thousand impressions. It is calculated to demonstrate the ad revenue generated from 1000 ad impressions. eCPM is the average number of multiple CPMs.
In simpler terms, eCPM gives you the combined average of all advertiser bids on your ad impressions.
Formula of eCPM
Example of eCPM
Let’s imagine that there were two campaigns on the publisher’s website.
The CPM for the first campaign was 1€, and the CPM for the second was 0.20€. Each campaign bought 1000 ad impressions.
In this case, the publisher generated a total revenue of 1.2€ (1€ + 0.20€) per 2000 (1000 + 1000) ad impressions. Therefore, the eCPM was 0.60€ (1.2€ / 2000 x 1000= 0.60€).
What is rCPM?
rCPM, also known as RPM, stands for real cost-per-thousand. The calculation of rCPM shows the average price of 1000 ad requests.
The main difference between eCPM and rCPM is that with rCPM the publisher’s revenue is based on total ad requests instead of ad impressions.
Therefore, rCPM takes into account the fill rate. rCPM is calculated as if all ad requests were filled, and if something wasn’t, it goes into the sum of revenues with a value of 0. Naturally, rCPM will always be lower than eCPM.
Ad request vs impression
An ad request refers to the number of times the website calls for an ad. It doesn’t mean that the ad will automatically be displayed. An ad impression defines the number of times an ad has been served and viewed by a user.
The reason why not all ad requests are filled with ad impressions is influenced by many factors, like user behaviour, bounce rate, ad load time, website loading speed, and more.
*If you use Google AdSense, you won’t be able to see how many ad requests you have received. Unless you use an ad server, for example, Google Ad Manager, you will only be able to see ad impressions. Publishers who have their own ad server can see rCPM metrics.
Formula of rCPM
Example of rCPM
Let’s imagine there was a campaign on the publisher’s website, which generated 1000 ad requests in total, and the eCPM price was 2€. However, the ads were only displayed 250 times. That means the publisher sold 250 ad impressions of the 1000 ad requests made.
From eCPM formula, we conclude that the total ad revenue generated by the publishers was 0.5€. Therefore, the rCPM was 0.50€.
What is Fill Rate?
Fill rate is the percentage of ad impressions your ad received, divided by the total ad requests and multiplied by 100%.
Fill Rate Formula
Example of Fill Rate
Again, let’s imagine the same ad campaign on the publisher’s website, which generated 1000 ad requests. However, the ads were only displayed 250 times. This means, only 250 ad requests were transformed into ad impressions. In this case, the publisher’s fill rate was 25%.
The fill rate is typically influenced by a lack of demand or a set minimum price floor. In this case, the publisher should use a passback or account for unfilled impressions as lost.
Which Metric Should You Choose for Comparison?
Overall, it’s advised to look at both eCPM and rCPM when evaluating your monetization performance.
For example, an SSP won the auction, but the user bounced away from the page before the ad had time to load, leaving the impression unfilled. This kind of ad discrepancy can be observed when comparing eCPM with rCPM.
If, however, you want to evaluate ad revenue from a specific monetization partner, choose the rCPM metric for comparison. If your rCPM is higher, your ad revenue will increase. Since rCPM includes fill rate value, your calculation will be more precise than if you were to use just eCPM.
Keep in mind that a high eCPM with a low fill rate equals a lower rCPM and total revenue. Hence, you cannot only rely on your eCPM because there is a possibility that your fill rate is lower than desirable.
Now that you know how eCPM, rCPM, and fill rate differ, the next step is to improve the value of each ad impression. And that’s exactly where Setupad can help!
By using header bidding wrapper, Setupad can increase the price of every sold ad impression by at least 30%. Our solution can deliver an ad to the page almost immediately when the ad request is triggered. Your total ad revenue will rise respectively. Test it out yourself by signing up!