What does a fill rate mean?

This term relates to display advertising, and can be used to quantify the effectiveness of either a sales team or a network at maximizing the number of ads shown by a site. The formula used here is very simple:

Fill Rate = Ad opportunities successfully filled / Total ad opportunities

A 100% fill rate is optimal; that means that every time there was an opportunity to show an ad to a visitor, one appeared. A fill rate of less than 100% means that a failure to show ads at every opportunity resulted in at least some lost income.

A missed ad opportunity occurs when a page loads but no ad appears in one or more of the open ad positions. This may occur for several reasons, including:

  • Lack of demand (i.e., there are no ads from direct deals or ad networks continuing for a spot)
  • Technical error / sub-optimal technical set-up

The link below includes some further reading for troubleshooting any apparent shortfalls in fill rate.

Most ad networks should be able to provide 100% fill rate on all ad requests made by publishers. If you are having issues with networks struggling to find demand for your available ad impressions, you may want to consider an alternative network.

Fill Rate vs. Coverage

Within Google AdSense, the term “coverage” is used to mean the same things as fill rate. Here’s how their help center describes this term:

For example, if you have 3 ad units on a page, you’ll generate 3 ad requests. If two of these ad units display ads and one displays no ads, the coverage for this page would be 66.67%. Likewise, if you have a search box, coverage of 80% means that an average of 1 query out of 5 shows no ads with the search results.

Calculating Fill Rate

Understanding fill rate is easiest through an example. Suppose that every page on a site includes a 728×90 leaderboard near the top. As such, we would expect that for every pageview, an ad impression is recorded.

If the site gets 500,000 pageviews and there are 475,000 ad impressions recorded, the fill rate would be 95%.

Ad Blocking

Fill rate doesn’t consider as that are not served due to visitors using ad blocking programs. There are a number of services that can be used to prevent ads from appearing when a page is loaded, which is obviously an undesirable event for the publisher. There are some recently-developed solutions that can help advertisers break through these ad blockers, including PageFair.

Maximize Fill Rate

There are many factors that hamper the occurrence of ads when you need them to.

External Factors

  • Location of traffic

publishers place-specific targeting options on their advertising campaigns to ensure they are shown to relevant prospects.

  • Device type

On average, publishers are more likely to serve adverts to users on a mobile device than a desktop. You have no control over which devices traffic use to access your site, and publishers often target ads on more popular devices and web browsers.

  • Advertising networks

Here are a number of advertising networks to pick from, with many having just a few publishers and campaigns. With few clients and limited daily budgets, smaller networks don’t have a large enough ad inventory to serve ads resulting in very low fill rates

Internal Factors

  • Optimizing website

An optimized website speeds this process up and serves the advert before the visitor has clicked on a new page or left. There are a number of ways to improve the response time of a website from picking a great hosting plan, choosing the right theme, and speeding up a website’s load time.

  • Ad blocking

Fill rate doesn’t take into account ad blocking software and can sometimes misrepresent your actual eCPM and fill rate. To ensure ads are served and seen by traffic, use a program like Page Fair to combat against ad blockers.

  • multiple Ad slots

Publishers often use a number of different ad sizes to get the most out of their campaigns. This also provides users with a better ad experience than showing them the same ad over and over again.


What does ad fill rate mean?

Fill rate is the percentage of ads “getting served” out of the total number of “ad calls” being requested on site/page

How do you calculate the ad fill rate?

To calculate the fill rate is just simply by taking the total number of ads served divided by the total number of ad request, then multiply with 100

How does ad fill rate affect eCPM?

A high fill rate indicates that ad responses were delivered regardless of the eCPM of the ad. Since more ads are displayed when having a high fill rate, more impressions are generated and therefore it is possible for the eCPM measurement to decrease