What is fill rate in advertising and how is it calculated?
How to calculate fill rate, what a low or high fill rate tells you, and why fill rate should always be read together with price.
Written by Samhub with the help of AI·Updated 13 Oct 2026·3 min readFill rate is the share of ad requests that return an ad. If 1,000 ad slots ask for an ad and 900 get one, the fill rate is 90%.
How to calculate fill rate
Fill rate = filled ad requests ÷ ad requests × 100
Example: 900,000 ÷ 1,000,000 × 100 = 90%
Illustrative numbers.
What the number tells you
| Fill rate | Often means |
|---|---|
| Low | Too little demand, floors too high or technical problems |
| High | Strong demand, or floors set too low |
| Uneven | Some placements or audiences lack demand |
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Balance fill and price
100% fill at a low price can earn less than 85% fill at a higher one. Watch fill rate together with eCPM and page RPM, and raise demand with audience data rather than lowering floors.
CPM uplift at Stampen Media after activating first-party audiences with Samhub.
Frequently asked questions
It depends on your setup and goals. Read it together with eCPM, not on its own.
No. Fill rate covers all ad requests. Sell-through rate usually covers inventory sold directly.
Higher floors reject more bids, which can lower fill but raise price.
Add demand partners, offer audience data and deals, and fix technical problems that stop ads loading.
Related terms
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