Amazon restock planning: days of cover, lead time and reorder point

Running out of stock on Amazon costs more than the missed sales. Ads keep spending on clicks that cannot convert unless you pause them, organic rank slips while the product is unavailable, and it can take weeks to recover. Overstock costs too: storage fees and cash tied up in boxes. Three numbers get the balance right.

1. Days of cover

Days of cover = units on hand (plus inbound) ÷ units sold per day. 600 units selling 20 a day is 30 days of cover. Use recent sales speed, such as the last 30 days, not last year's average: a product whose sales doubled runs out twice as fast.

2. Lead time and the reorder point

Lead time is the number of days from placing the order with your supplier until the units can be sold at Amazon: production, freight, customs and Amazon's receiving. The reorder point is the stock level at which to order again:

Reorder point = units sold per day × (lead time + safety days).

Safety days cover a late shipment or a sales jump; 7 to 14 days is common, more for long supply chains or best sellers.

3. How much to order

Order quantity = units sold per day × (lead time + safety days + days a delivery should last) − units on hand and inbound, rounded up to whole case packs. The days a delivery should last balance ordering often (more shipments, less storage) against ordering rarely (fewer shipments, more storage and cash tied up).

A worked example

A product sells 14 units a day. Lead time is 45 days, safety stock 10 days, and each delivery should last 30 days. 420 units are at Amazon and 200 are inbound: 620 units, 44 days of cover. The reorder point is 14 × (45 + 10) = 770 units, so it is already time to order. The order is 14 × (45 + 10 + 30) − 620 = 570 units, rounded up to 576 with a case pack of 24. Try your own numbers in the reorder point calculator.

Plan for sale events

Prime Day, Black Friday, White Friday and the holiday season can multiply sales for days. Raise the daily sales figure for the event period when you plan the order before it, and check Amazon's inbound deadlines for the event.

Watch the warning signs

• Stranded units: in stock but not for sale, usually a listing problem. Fix them before ordering more.
• Aged and overstocked units: candidates for a deal or a liquidation campaign.
• Ads on products about to run out: lower budgets when stock will not last until the next delivery, and pause ads when it is gone.

SellerPilot calculates days of cover and reorder quantities for every product from live sales and stock, plans FBA shipments in case packs, and pauses ads when stock runs out. More about the restock planner.