Days of Cover on Amazon: How to Calculate It and Why It Prevents Two Different Fees
Days of cover tells you how many days your current FBA inventory will last at your current sales rate. Too low: low inventory level fee. Too high: storage utilization surcharge. The right number is 28–90 days depending on your supply chain.
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Run the numbers →What is days of cover?
Days of cover (DOC) = Units in FBA / Daily sales velocity
At 500 units in FBA and 20 units/day sold: DOC = 500 / 20 = 25 days.
Amazon also calculates weeks of cover (WOC) = Units in FBA / Weekly sales velocity.
25 days ≈ 3.6 weeks of cover. Amazon's target zone based on fee thresholds: 4–26 weeks of cover. Below 4 weeks: risk of low inventory level fee. Above 26 weeks: risk of storage utilization surcharge.
The right days of cover by supply chain type
Domestic supplier with 2-week lead time: target 28–45 days of cover (2× lead time + buffer). China import with 8-week lead time: target 70–100 days of cover (lead time + 30-day buffer). AWD program: can target lower FBA DOC (4–6 weeks) since AWD replenishes automatically.
The key: your DOC should be greater than your inbound lead time by a safe margin. If your lead time is 45 days and you have 30 days of cover, you'll hit a stockout before new inventory arrives.
Frequently asked questions
How do I find my days of cover in Seller Central? ▾
Seller Central > Inventory > Inventory Planning > Restock Inventory. The "Weeks of Cover" column shows current WOC by ASIN. Amazon also shows "Days of Supply" in some views.