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What Is Ad Fill Rate?

Ad fill rate is the rate at which an ad network is able to fill its ad requests. This glossary entry explores the most common definition of fill rate from a publisher’s perspective; however, each ad network defines it differently.

Fill rate in advertising is complex; it takes into consideration multiple stages of the programmatic funnel, including show rate, bid rate, and win rate. Publishers can calculate this rate overall for their ad placement in the app or per ad network to measure and compare their performance within the mediation landscape.
Key Takeaways
  • To calculate this rate, you need to divide the total ad impressions by ad requests of an app and multiply this by 100
  • Publishers should aim for an rate of 85% or higher to maximize their revenues
  • Publishers can measure fill rate for their app overall and per demand source

What Contributes to Fill Rate?

As mentioned, ad fill rate comprises multiple factors and actions that occur at different stages of the funnel.

funnel showing all events that contribute to fill rate in advertising
  1. The publisher’s app sends an ad request via mediation and/or ad exchange
  2. The ad exchange/mediation platform that receives this request sends a bid request to demand sources
  3. Bid responses are sent back to the mediation platform or ad exchange 
  4. The platform decides the winning bid
  5. In an ideal scenario, the end user sees the winning ad

Publishers measure this rate by looking at all stages from the ad request to showing the ad, including the various stages in between. What contributes most to the final rate is how demand partners perform and whether they respond to ad requests.

How Do You Calculate Ad Fill Rate?

To calculate fill rate in advertising, publishers need to divide the number of ad impressions an app shows by the number of ad requests from the app. They then multiply this by 100.

The fill rate advertising formula is as follows: 

fill rate advertising formula written down (total ad impressions divided by ad requests x 100)

So, for example: An app’s total available ad impressions are 90,000 and it receives 100,000 ad requests. The app would have a fill rate of 90 percent.

Why Is Fill Rate Important?

Marketers measure this rate to ensure they are effectively monetizing their ad inventory. Since publishers get paid for an ad impression shown in their app, it’s directly related to revenue. A higher rate means more impressions and more revenue for a publisher. Keeping a close eye on this metric is extremely important. 

A high rate of 85 percent and over means that a high percentage of ad requests have been filled with ads. A low rate means that a low percentage of ad requests are filled with ads. 

There are various factors that contribute to poor fill rates – all of which publishers must look out for to keep their revenue numbers on track. These factors include:

  • technical errors connected to calling an ad provider (for example, mediation platform)
  • long ad loading times
  • lack of demand, for example, because of unpopular GEOs or old user devices/OS versions that aren’t supported by demand partners

Looking at fill rate helps publishers compare the performance of demand sources. Publishers might look at how many impressions out of ad requests a demand source can fill. If publishers know that the ad networks they work with have a low fill rate, they need to carry out certain measures to boost it.

How Do You Optimize Fill Rate?

There are various measures publishers can take to optimize their ad fill rate. These include the following: 

  • Attract better demand sources: Publishers should analyze fill rate per ad source and continuously search and test for what works best per app and placement.
  • Optimize ad placement: A low rate could mean low-quality users and ad impressions – and that the ad placement doesn’t convert well. Publishers could optimize their placement to increase quality and attract better users by trying different user scenarios and places where/when to put an ad.
diagram showing how to increase fill rate through better demand sources and better ad placements


Monitoring fill rate is important for publishers to know how effectively they are monetizing their ad inventory. 

Although optimizing this rate is important for publishers in order to maximize their revenue from advertisers, they should also focus on high-quality demand sources that are able to deliver high fill rates.


What Is Ad Fill Rate?

Each ad network defines this metric differently. However, the most common definition from a publisher’s perspective is that it’s the rate at which an ad network is able to fill its ad requests.

How Do You Calculate Fill Rate?

To calculate a fill rate in advertising, publishers need to divide the number of impressions an app shows by the number of ad requests from the app. They then multiply this by 100.

How Do You Optimize Your Fill Rate?

Publishers should aim for rates of 85 percent and higher. To do this, they should aim to attract better demand sources and optimize ad placement to increase quality and attract better users.

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