Introduction
If you’re running ads on your website, you’ve probably heard this term:
👉 Fill Rate
But what does it actually mean?
And more importantly:
👉 Why does it matter for your revenue?
The truth is, even if your CPM is high, a low fill rate can kill your earnings.
In this guide, we’ll break it down in simple terms.
What is Fill Rate?
Fill rate is the percentage of ad requests that are successfully filled with ads.
Formula:
Fill Rate = (Filled Impressions / Total Ad Requests) × 100
Example
Let’s say:
- You have 100,000 ad requests
- Only 70,000 ads are served
👉 Your fill rate = 70%
Why Fill Rate Matters
Fill rate directly impacts your revenue.
👉 Low fill rate = empty ad slots = lost money
Even if your CPM is high:
❌ no fill = no revenue
What Causes Low Fill Rate?
Several factors can reduce your fill rate:
1. High Floor Prices
If your floor is too high, buyers won’t bid.
2. Low Demand
Limited demand = fewer bids
3. Geo Traffic
Some countries have lower demand
4. Technical Issues
Incorrect setup in ad server
How to Increase Fill Rate
Here are proven ways:
1. Adjust Floor Prices
👉 Don’t set unrealistic floors
👉 Find the balance between CPM and fill
2. Increase Demand Sources
👉 Use multiple demand partners
👉 Enable competition
3. Use AdX (if available)
AdX increases competition and improves fill.
👉 Learn how it works:
👉 What is Google AdX and How Does It Work?
4. Optimize Ad Requests
👉 Reduce duplicate requests
👉 Improve loading logic
5. Use Backfill (AdSense)
AdSense can fill unsold inventory.
👉 Compare here:
👉 AdSense vs AdX
Fill Rate vs CPM
These two are connected:
👉 High CPM + Low Fill = bad
👉 Low CPM + High Fill = also bad
👉 The goal:
✔ balanced optimization
Final Thoughts
Fill rate is one of the most overlooked metrics in advertising.
But improving it can instantly increase your revenue.
If you’re serious about monetization:
👉 Track your fill rate
👉 Optimize it continuously