What is Fill Rate?

Fill rate is a crucial metric in digital advertising that measures the efficiency of an ad network or publisher's ad inventory. It is expressed as a percentage and represents the ratio of ads successfully served to the total number of ad requests made by a website or mobile application. For publishers, a high fill rate is generally desirable as it indicates that their inventory is being utilized effectively to generate revenue.

How to Calculate Fill Rate

The formula for calculating fill rate is straightforward: divide the total number of ads served (filled) by the total number of ad requests, and then multiply by 100.

Formula: (Ads Filled / Ad Requests) × 100 = Fill Rate (%)

For example, if your website requests 1,000 ads and the ad network serves 900 ads, your fill rate is 90%.

Why Fill Rate Matters for Publishers

Monitoring your fill rate allows you to identify bottlenecks in your monetization strategy. If your fill rate is low, it means you are missing out on potential revenue because your available ad space is remaining empty. Common causes for a low fill rate include high floor prices (eCPM), technical latency, lack of advertiser demand for specific geographic regions, or ad blocking software used by visitors.

Frequently Asked Questions

What is a good fill rate? While a 100% fill rate sounds ideal, it is rarely achieved due to technical discrepancies. Most publishers aim for a fill rate between 85% and 95%. Sometimes, a lower fill rate with a higher eCPM (cost per thousand impressions) is more profitable than a 100% fill rate with very cheap ads.

How can I improve my fill rate? You can improve your fill rate by implementing header bidding, reducing price floors to attract more buyers, optimizing site speed, and diversifying your ad networks to ensure there is always a "backfill" option.