When managing ad monetization through Google Ad Manager (GAM), two key metrics often confuse publishers: match rate and fill rate. Both are essential for understanding how well your ad inventory performs. However, they measure different parts of the ad delivery process.
In this article, we’ll explain the difference between match rate and fill rate in Google Ad Manager report, how they are calculated, why they matter, and how you can optimize both for better ad performance.
What Is Match Rate in Google Ad Manager?
Match rate represents the percentage of Ad Exchange ad requests that were valid and eligible to enter the auction.
Not every ad request gets passed to buyers. Some requests are filtered out due to policy issues, missing consent, incorrect formatting, or unsupported devices. The match rate tells you how many of your total AdX requests were actually qualified to be auctioned.
Match Rate Formula:
Match Rate (%) = (Matched Requests / Ad Exchange Requests) × 100
Example:
- Ad Exchange Requests: 10,000
- Matched Requests: 9,000
- Match Rate = (9,000 / 10,000) × 100 = 90%
Why Match Rate Matters
If your match rate is low, it means many of your ad requests are being dropped before they even enter the auction. This leads to wasted inventory and lost revenue opportunities.
What Is Fill Rate in Google Ad Manager?
Fill rate measures the percentage of ad requests that were successfully filled with ads.
Even if a request enters the auction, there’s no guarantee that an advertiser will win and serve an ad. Fill rate helps you understand how often your available ad slots are actually showing ads.
Fill Rate Formula:
Fill Rate (%) = (Ad Impressions / Ad Requests) × 100
Example:
- Ad Requests: 10,000
- Ad Impressions: 8,000
- Fill Rate = (8,000 / 10,000) × 100 = 80%
Why Fill Rate Matters
A low fill rate means fewer ads are being shown, which directly affects your revenue. It may indicate weak demand, overly high floor prices, or competition issues.
Difference Between Match Rate and Fill Rate in Google Ad Manager Report

Now that you understand both metrics, let’s compare them side-by-side:

Understanding the difference between match rate and fill rate in Google Ad Manager report helps you identify whether the problem lies in your ad setup or in the demand from advertisers.
What Are Ad Exchange Ad Requests?
An Ad Exchange ad request is a call made by your site or app to Google AdX asking for an ad to be served. This request includes information like:
- Ad unit ID
- Page or app content
- User device and location
- Consent signals (GDPR, CCPA)
- Supported ad sizes
However, not every request becomes a matched request. AdX may discard the request due to policy violations, missing data, or unsupported ad formats.
What Is Ad Exchange Ad Serving?
Once a matched request enters the auction, it’s sent to potential buyers. If a buyer bids and wins, an ad is served to the user. This is called Ad Exchange ad serving.
This process results in an ad impression, which is then counted toward your fill rate.
How Are Match Rate and Fill Rate Calculated?
Let’s simplify the flow and math:
- User visits your site/app.
- Your ad tag sends a request to Google AdX.
- GAM validates the request.
- If valid → Matched Request
- If invalid → Dropped (lowers match rate)
- Matched requests go into an auction.
- If a buyer wins and ad is served → Impression
- Impression is counted → Affects fill rate
Match Rate Formula:
Match Rate (%) = (Matched Requests / AdX Requests) × 100
Fill Rate Formula:
Fill Rate (%) = (Ad Impressions / Ad Requests) × 100
Keep in mind: AdX requests and ad requests may differ depending on your setup (AdSense, Open Bidding, direct campaigns).
Common Causes of Low Match Rate
No Consent Signals
In GDPR and CCPA zones, requests without proper consent are dropped.
Incorrect Ad Unit Sizes
Ad slots must match the defined size in Google Ad Manager.
Unsupported Platforms
Requests from devices or browsers not supported by AdX are ignored.
Blocked Content
Pages violating Google’s ad policies get rejected at the request level.
Common Causes of Low Fill Rate
High Floor Prices
If your minimum CPM is too high, buyers may not bid.
Limited Demand Partners
If you rely only on AdX, you miss out on other advertisers.
Poor Page Speed or Layout Shifts
Slow pages or unstable ad placements affect viewability and delivery.
Time and Geography
Late-night traffic or users from low-demand regions see fewer ads.
How to Improve Match Rate
- Use a Consent Management Platform (CMP)
- Regularly validate your ad tags
- Update all ad unit sizes in Google Ad Manager
- Ensure content is policy-compliant
- Monitor geo settings and exclude unsupported locations
How to Improve Fill Rate
- Lower your floor price to allow more bids
- Enable Open Bidding to add more demand sources
- Use AdSense as backfill if no bid wins
- Avoid excessive page latency or layout shifts
- Enable collapsing for empty ad slots to improve UX
Real-World Example
Let’s say your site receives 100,000 ad requests per day.
- 90,000 of these are valid and sent to buyers → Match Rate = 90%
- 75,000 of those result in actual ads shown → Fill Rate = 75%
That means 15,000 matched requests did not get filled, and 10,000 requests were discarded before auction.
Final Thoughts
Understanding the difference between match rate and fill rate in Google Ad Manager report is key to boosting your ad revenue. Match rate shows how many of your ad calls were valid. Fill rate reveals how many ads were actually shown.
Optimizing both gives you a stronger monetization foundation. Focus first on improving your match rate through better tagging and compliance. Then, work on boosting fill rate through pricing strategy and adding more demand.
Track these metrics consistently, and you’ll start seeing better performance, more impressions, and higher earnings from your ad inventory.
FAQs
Why are my match rate and fill rate both low?
You may have issues at both ends—technical errors causing invalid requests, and poor advertiser demand or high floor prices.
Can match rate be higher than fill rate?
Yes. Match rate only measures eligibility to enter the auction. Fill rate depends on whether a bid wins and an ad is shown.
What is a good match rate?
A match rate above 90% is considered healthy. Anything below 80% needs attention.
What is a good fill rate?
Aim for a fill rate of 80% or more. Lower than that may indicate pricing or demand issues.
Do these metrics apply only to Google AdX?
Primarily, yes. Especially match rate is specific to Ad Exchange. Fill rate can apply to overall ad requests across networks.
How often should I track these metrics?
Ideally, monitor them daily. Look for sharp drops or patterns weekly for deeper analysis.
What tools can help improve these metrics?
Google CMP for consent
Google Publisher Console for tag validation
AdSense and Open Bidding for fill optimization
Does low match rate affect revenue more than fill rate?
Both matter. Low match rate means your inventory isn’t even entering the auction. But low fill rate means you’re not monetizing what was available.