What Is Fill Rate? Formula and Benchmarks

What is fill rate?

Fill rate is the share of ad requests from your website or app that were answered with an ad. If your app asks for 1,000 ads and 850 come back, your fill rate is 85%. The other 150 requests went unfilled, which means an empty slot or a fallback and no earnings from that opportunity.

Fill rate is a publisher metric. It tells you how much of your available inventory advertisers actually bought, and it is one of the first numbers to check when revenue drops without an obvious change in traffic.

The fill rate formula

Fill rate = (filled ad requests ÷ total ad requests) × 100.

Two details decide whether your number means anything. First, count requests at the same point every time, for example at the ad server rather than in your code. Second, decide whether a request that received an ad which was never shown counts as filled. That difference is why ad platforms often split the idea into several metrics.

Fill rate vs match rate vs show rate

Google AdMob, for example, reports match rate rather than fill rate and defines it as matched requests divided by requests, times 100. Show rate is commonly calculated as impressions divided by matched requests. A good match rate with a poor show rate usually points to your own app: ads are loaded but never shown because the user left, the placement was never reached, or the ad expired first.

Why fill rate drops

• Country mix. Advertisers compete hardest for users in high-income markets. Traffic from countries with fewer buyers fills less often. See Tier 1, 2 and 3 countries explained.
• Price floors. A floor rejects bids below a set price. Google’s AdMob help lists high eCPM floors as a common reason for a low match rate.
• Blocked categories and advertisers. Every block removes bidders. AdMob’s help notes that blocking any ad lowers match rate because it reduces competition.
• Audience restrictions. Apps directed at children have a smaller pool of suitable advertisers, and AdMob lists this as a reason for lower match rates.
• New apps and ad units. AdMob notes that demand can be reduced for up to a week while traffic quality is evaluated.
• Seasonality. Advertiser budgets rise and fall through the year, so fill can move without any change on your side.
• Technical errors. Timeouts, outdated SDKs, and wrong ad unit IDs count as unfilled requests too.

Fill rate benchmarks: what is a good fill rate?

There is no single benchmark worth copying. Fill rate depends on the ad format, the countries your users are in, your floors, your mediation setup, and even on how your platform counts a request. Two apps can both be healthy with very different numbers, and published averages rarely say how they were measured.

A more useful approach is to build your own baseline:

1. Record fill rate by format and by country for four weeks.
2. Note the normal weekly range for each combination.
3. Investigate when a combination falls clearly below its own range, not when it is below someone else’s average.
4. Always check revenue per user in the same period before you act.

Why a lower fill rate can earn more

This is good news for publishers, because floors are a setting you control. Fill rate and price pull in opposite directions. Lower your floors and more requests fill, but at lower prices. Raise them and fewer requests fill, at higher prices. The right setting is the one that earns the most per user, not the one with the highest fill.

That is why fill rate should always be read next to eCPM and RPM, and why eCPM and EPC are better guides to what a placement earns.

Fill rate on an offerwall

An offerwall does not answer one request with one ad. It shows a list of offers, so “fill” means something slightly different: whether a user who opens the wall finds offers worth doing. Three things decide it:

• Offer availability by country and device. Advertisers choose where their offers run, so a user in a country with few campaigns, or on a device an offer does not support, sees a shorter list.
• Your currency settings. On Sharklio, offers that would give the user 0 after your conversion rate, split, and rounding are not shown. A rate that is too low hides the smallest offers. How to set your virtual currency exchange rate covers how to avoid that.
• Budgets and caps. Advertisers set daily budgets and caps, so the list changes during the day as some campaigns pause and others start.

On an offerwall, the better health metrics are the share of users who open the wall, the share who start an offer, and earnings per active user. Offerwall placement and Offerwall vs rewarded video explain how to improve those.

How to improve fill rate

Start with the fixes that cost nothing, and check revenue per user after each one.

1. Check for errors first. Timeouts and misconfigured ad units look like low demand.
2. Review floors country by country. A floor that suits one market can starve another.
3. Unblock categories you do not really object to, since every block costs competition.
4. Add demand sources. More bidders, or a second monetization format such as an offerwall, gives users something useful when an ad slot would stay empty.
5. Request ads when you will show them. Loading too early wastes requests and lowers show rate.

Frequently asked questions