Definition of Fill Rate
The percentage of ad pageloads that are filled by display ads.
Fill Rate in Depth
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%.
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.