Ad fill rate: What is it | How to improve | How to calculate | Is 100% fill rate good | And everything else publishers want to know about it.

Most publishers rely on advertising as a primary source of revenue, however, the growing competition for ad dollars has made it challenging for publishers to generate profits.

In light of this, publishers have had to explore a number of alternative methods of revenue generation such as – 

  • Charging for access to premium content. 
  • Incorporating alternative advertising strategies. 
  • Crowd-funding to raise money from fans or supporters. 

In fact, according to a study by Siteefy, every minute, 175 new websites are created, making the competition more fierce. 

In this competitive landscape, ad fill rate is a crucial metric that measures the percentage of ad impressions that are successfully delivered to a website or app. 

By closely monitoring their ad fill rate, publishers can make informed decisions to optimize their advertising opportunities and increase their revenue. 

Let’s take a closer look at what is ad fill rate and how to calculate it.

What Is Ad Fill Rate?

Ans. As you might know, publishers strive to sell as many ad impressions as possible at the best price. Of course, the intent is to make money. And this is where ad fill rate comes into equation.

Ad fill rate is a metric, which is ued to measure the percentage of an ad impression successfully served to a website or an app. 

Technically speaking, ad fill rate is the percentage of ads ‘getting served’ out of the total number of ‘ad calls’ being requested on a site/page.

How great or average is your ad fill rate helps you decipher the proficiency of your ad network. Also, how much you’re monetizing (or not monetizing) the impressions on your website.

Let’s understand the same in a simpler way.

High ad fill rate – High ad fill rate means that a large percentage of ad requests are being fulfilled with advertisements.

Low Ad Fill Rate –  Low ad fill rate means that only a small percentage of ad requests are being fulfilled with advertisements.

All About Ad Tech – Scaling Ad Revenue

How To Calculate Ad Fill Rate?

Ans. Let’s do some math:

For instance, your apartment has space for 20 tenants. Out of 20, only 17 tenants are residing in and paying you the rent. Now here the catch is, we’re not counting the number of spaces (ads) you sold.

For the reason that you managed only 17 paying tenants in a space of 20, your fill rate (17 divided by 20 times 100) amounts to 85%.

Likewise, let’s say your website has the bandwidth to serve 2,00,000 impressions but ends up serving 1,75,000 impressions. So by applying the same formula as above, your ad fill rate will be 87.5%.

→ # of ads delivered ÷ # of ad calls made x 100 = Ad fill %

In case you get 1,85,000 impressions the next day, your ad fill rate will rise from 87.5% to 92.5%. (which may or not be good news. I’ll tell you why)

Why Am I Not Getting 100% Ad Fill Rate?

Technical Errors

You might have heard “technical errors” as an excuse for a lot of things. In daily life, from a fixed-line broadband issue at your home to data syncing issues in your work CRM, they all say, “Apologies, we’re facing a technical problem.”

Similarly, the loose ends in your website are big-time-contributors affecting your ad fill rate. The challenge here is, some technical errors might be in your hands. While there could be many that you might just not be able to identify in the first place.

Nevertheless, you might have to deal with them, today or tomorrow. Some more typical technical errors are latency, insufficient demand, mobile/device/browser incompatibility, etc. So go, fix them.

Page Latency

Yes, page latency can affect the ad fill rate. If the page takes too long to load, the ad server may not be able to fill the ad space in time, resulting in an ad not being shown. 

This can result in a lower ad fill rate and decreased revenue for the publisher.

It’s important to monitor and optimize the page loading speed to ensure that the ad space is filled and maximum revenue is generated.


Ads may not always display consistently across all browsers, devices, or operating systems due to compatibility issues. Generally, this happens due to outdated browsers or outdated operating systems that need to be updated.

Moreover, you need to make sure that ads are run correctly on mobile devices. It’s because an increasing number of advertisers are targeting people with mobile ads. Using the right format will ensure that your ads display correctly on various devices and increase the chances of reaching your target audience.

This will help to improve your ad’s fill rate and ultimately enhance your overall advertising performance.

How To Improve Ad Fill Rate?

Ans. You may have been waiting for this, so here it is. There are many factors which hamper the occurrence of ads when you need them to. These are technical errors which you may or may not be able to tame. See for yourself:

  1. Work on website/page load time

    Users don’t wait. Because you run a website, I’m assuming you know that every second counts. Especially in case of ad impressions, timely rendering is one of the most dominant factors that make you lose impressions, hence revenue.

    Now load time is something you may be able to decide. This is time for you to look up to your ops team who should be able to help you achieve a load time which is favorable.

    This had to be next. Why? Understanding how the demand and supply cycle works, you might observe, there are times when you’re unable to meet sufficient demand to fill your ad slots.

  2. Get started with Header bidding

    Result? You leave a blank impression, leaving money on the table. This is exactly why publishers are ditching old-school methods like daisy-chaining and publishers waterfall and shifting to header bidding.

    The point is, these old processes can’t promise great CPMs, are relatively less automated, and add on to your load time.

  3. Go for location based targeting

    Next, you can go one step ahead by targeting users not just by interest, industry, or niche, but also their geography. If you have no idea yet, your google analytics account or any tracking you use should help.

    All you need to do is figure out the regions (city or country) bringing you the maximum traffic. Having specifically targeted regions is likely to get more traffic, hence likely to make more ad calls leading to more ad impressions

  4. Switch ad sizes when required

    Change is constant. Okay this may sound metaphorically vague here, but heck this is true. Let’s say you might prefer a 300×600 ad size as your data shows that it has brought the max. CTR.
    However, you need to have the flexibility of different ad sizes in case your primary sized ad slot isn’t in demand. A backup size 300×250 here can help you. The leverage of flexi ad sizes is they let you fulfill the demand and achieve a better ad fill rate faster

  5. Deal with ad blocking

    Ad blockers are the scariest. It’s like, you follow all rules, stay compliant, execute all good practices, but yet you get blocked by your users. And this is something you can’t even control.

    What ad blockers do sometimes is they block the ad network instead of the ad call. Meaning, your ad request is made, but the blocker did not let your ad appear.

    Although with solutions like pagefair and ad block recovery, it has become possible to save some impressions and revenue while not disrupting the users’ experience on your website.

Also Read – How Top Publishers Organize their Ad Stack – AdPushup

What is the Average Industry Ad Fill Rate?

Ans.  Usually, ad networks promise anywhere between 25-55% ad fill rate. This really means you need to change your ad network and switch to someone more ambitious. This generally means they have plenty of supply, but not enough demand.

Largest ad networks like AdSense give you the bandwidth to scale your ad fill rate up to 100%. Once set to 100, their algorithm tries its best to make you achieve 100% fill and impressions.

However, they have their own rationale on why you should/shouldn’t have 100% ad fill rate? (up next)

Does 100% Ad Fill Rate Imply 100% Potential Revenue

Ans. This is a question of dilemma. Honestly, it’s just easy to say that “Yes, a 100% ad fill rate is the best thing.” Since impressions = revenue in the publisher world, achieving 100% of it is like a dream come true.

But a 100% ad fill rate is not always good. In the ad tech world, things don’t always run so easily. And neither does the logic behind it. Sometimes, with the intent to uplift your ad fill rate, you might end up seeing your CPMs falling.

We know every lost impression means a loss of potential revenue. Therefore what happens is, you may try to display all your ads (once you fix the technical ends) but it has to be regardless of how much your impressions will value.

Sometimes, a high ad fill rate yields high CPMs. However, sometimes publishers compromise their CPMs to keep their ad placements filled all the time. In such cases, the ad fill rate increases, but you never know what value your impression will bring you ($0.2 CPM or $2 CPM).

How To Optimize Ad Fill Rate (Whether 100% Or Less)?

Ans. This is a myth that 100% always wins. In the case of publishers, some numbers indicate ー the least, the best. In the above logic, you may have noticed how a 100% ad fill rate can sometimes take your CPMs down.

Thankfully, the ‘ad balance’ feature from AdSense gives control to publishers’ hands. How does it work? You, the publisher can set the percentage to which you want to display ads.

For instance, if you want you may choose to show only 75% of your ads instead of the whole 100%. The intelligence of AdSense is that it’ll choose the highest-yielding ads for you. The ultimate benefits are:

  • Only your highest-yielding show
  • Your ads are monetized optimally
  • Your site experience improves with lesser ads

The Crux

Publishers shouldn’t just be aiming for increasing their ad fill rate. The effort should also be focused on strategizing targeting, ad placement, and website improvement for revenue generation.

The outcome of all efforts should be a nicely done user experience, opportunities for high yields by going for the highest CPMs and optimizing ad network performance to monetize the website ad inventory.

Furthermore, chasing after a 100% rate should not always be your preference. Attracting quality buyers to fill the ad space should also be at the top of your priorities. For the same reason, Google has also introduced Adblance, which ensures that publishers received enough advertisers without compromising on the ad quality.


1. What exactly is an ad fill rate?

Out of all the ad requests sent to an ad server, the “ad fill rate” represents how many of your ad units were served. You can determine how efficiently your inventory is being used by looking at the ad fill rate.

2. What is a good fill rate?

In general, companies maintain a fill rate of about 85%-95%. Ideally, you should aim for a fill rate between 97% and 99%.

3. What is programmatic fill rate?

The fill rate is the percentage of ad requests that are fulfilled by the ad networks you use. Calculated by dividing the number of ad impressions an app actually serves by the number of times it requests an ad.


Deepak has a keen eye for detail and a deep understanding of the ad tech landscape. Whether it's through in-depth articles, thought-provoking insights, or compelling storytelling, he’s dedicated to helping people navigate the complex world of ad tech with the simplicity of his words.

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