Fill rate is the percentage of available ad inventory that is filled with paying advertising. If your FAST channel has 8 minutes of ad break time per hour and 55% of that is filled with paid ads, your fill rate is 55% — you earn revenue on 4.4 minutes and leave 3.6 minutes unfilled (served as house ads, default slates, or silence). Fill rate is the primary revenue lever for FAST publishers because it directly determines how much of your available inventory earns money.
Fill rates vary significantly by market maturity. Established US FAST channels on major platforms achieve fill rates of 70–80% on a weighted-day basis, with higher fill during peak viewing hours. India FAST channels in 2026 realistically expect lower fill — industry estimates and comparable India CTV programmatic behaviour suggest 30–55% weighted average fill is achievable in the first year. This is a structural limitation of thin programmatic demand in India, not a reflection of content quality. Fill rates will improve as India's CTV programmatic ecosystem develops.
How to improve FAST fill rate in India
- Connect multiple SSPs: More demand sources means more auction competition and higher fill.
- Calibrate floor prices: High floors suppress fill. Set conservative floors initially; raise them as auction depth increases.
- Use house ads for unfilled inventory: House ads prevent dead air, maintain viewer experience, and allow cross-promotion of your content.
- Add backfill partners: A secondary ad network that guarantees fill at a lower CPM ensures no inventory goes completely unsold.
- Pursue direct deals for prime time: Direct-sold inventory is guaranteed fill at negotiated CPMs, eliminating auction uncertainty for high-value slots.
Track effective CPM (eCPM), not just fill rate
Fill rate alone does not tell you whether you are maximising revenue. A 90% fill at INR 150 CPM may earn less per hour than 55% fill at INR 350 CPM. Track eCPM — total revenue divided by total impressions served — to understand your true revenue efficiency. Optimise for the combination of fill rate and CPM that maximises revenue per hour (RPH), not for either metric in isolation.
Full guide
For a complete explanation, read: FAST channel fill rates and unsold inventory: how to maximise revenue