Understanding eCPM fluctuation

eCPM is the effective cost per thousand impressions. eCPM is an estimate of the revenue you receive for every thousand ad impressions. eCPM is calculated as (Total Earnings / Impressions) x 1000.

Understanding the impact of eCPM changes

Your estimated total earnings are based on the average eCPM times the total impressions. That being said, if lower eCPM allows higher impression counts, your estimated earnings may actually increase. You should monitor the estimated earning and impression trend to better understand the impact of your eCPM changes with a holistic view.

Factors that might affect eCPM

Depending on your monetization strategy or market factors, the eCPM could fluctuate. Note that the metric is not the only factor that leads to your estimated earnings change. You should monitor your impressions, eCPM, ad request numbers, match rate and other important reporting metrics to determine your monetization strategy. 

• Changes in market trends: eCPM is highly dependent on the market and platform. (i.e. eCPM in Singapore can be increasing, while in Brazil it might be going down in a particular time period.) There are also global trends affecting CPC/eCPM. 
• Blocking too many categories: Blocking ads and categories affects the auction and therefore the CPC. The bigger the category blocked, the bigger the effect. Note that blocking one ad is unlikely to have a significant impact, but as the number of blocks builds up, it can cause a sizable impact on the revenue.
• eCPM price floor change: Changing your eCPM price floors usually affects your average eCPM. If you cancel or lower the optimized price floor settings, it can result in many low bids for your inventory, resulting in lower eCPM.

Tools and guidance for improving performance

• Take Seasonality in mind: Check your eCPM trends in reporting with a longer period of time, year over year, month over month, and week over week view to verify if there's a seasonal change of your eCPM. If it's seasonal, that's likely outside of your control. However, you can be well-prepared with the seasonality checklist if you anticipate rising trends coming.

• Review recent changes: Review the inflection point of ads performance metrics like match rate, eCPM, impressions, and estimated earnings in your Ads Activity report and compare it with the recent changes you made in your AdMob account in change history. Consider reverting the setting if it leads to unexpected fluctuation. 

• Adjusting category blocking: By allowing all ad categories to appear, you could potentially improve your earnings because more advertisers can bid on your app’s inventory, and help improve your eCPM. If you need to, you can disable specific subcategories without over blocking.

  To minimize blocking, go to the "Blocking controls" tab in your AdMob account and switch the categories to "Allowed."

• Increase bidding pressure in AdMob Mediation: AdMob Mediation lets you expand advertiser demand to include third-party networks, including bidding and waterfall ad sources. This allows you to drive more competition to your ad inventory and to ensure you find the best available ad sources to fill the requests.

• Other useful tools and resources: AdMob provides several tools and guidance for monitoring and testing changes to your apps that can be used to improve monetization performance:

  • Implementation guidance

  • Mediation A/B Testing

  • Firebase A/B Testing

  • Reporting

    • Ads Activity: track ads performance metrics like match rate, eCPM, impressions, and earnings.
    • eCPM trends: monitor eCPM benchmarks by app category, platform, country, and ad format.