What is Fill Rate?
The percentage of ad requests that are successfully filled with ads, indicating the availability of ad inventory.
Fill rate is the percentage of ad requests that are successfully filled with ads by an ad network or exchange. It measures the availability of ad inventory and the ability of ad networks to serve ads when requested. A 100% fill rate means every ad request receives an ad, while a 70% fill rate means 30% of requests go unfilled.
Why It Matters
Fill rate directly impacts revenue potential - unfilled ad requests represent lost monetization opportunities. A low fill rate can indicate issues with ad network setup, targeting parameters, or insufficient demand for your app's audience. For publishers, monitoring fill rate helps optimize ad stack configuration and identify the most reliable demand sources.
How to Calculate
Fill Rate = (Ad Requests Filled ÷ Total Ad Requests) × 100. For example, if you made 10,000 ad requests and 8,500 were filled with ads, your fill rate would be (8,500 ÷ 10,000) × 100 = 85%.
Industry Benchmarks
| Category | Average | Good Performance |
|---|---|---|
| Premium Ad Networks | 85% - 95% | 95%+ |
| Mediation Platforms | 90% - 98% | 98%+ |
| Direct Sales | 70% - 85% | 90%+ |
Best Practices
Use mediation platforms to maximize fill rates by accessing multiple demand sources. Set appropriate floor prices that don't overly restrict inventory. Monitor fill rates by geography, device type, and time of day to identify patterns. Implement multiple ad networks with waterfall optimization to ensure backup demand.
Examples
A mobile game notices 60% fill rate during off-peak hours (2-6 AM) versus 95% during prime time, leading them to adjust floor prices dynamically. A news app improves fill rate from 78% to 94% by adding three additional demand sources through mediation.
Notes
Fill rate should be balanced with eCPM - a 100% fill rate with very low eCPM may generate less revenue than an 80% fill rate with higher-paying ads. Geographic differences in fill rates are common, with tier-1 countries typically having higher fill rates due to greater advertiser demand.