Amazon FBA restock calculator
When to place your next order with the supplier, and how many units, so new stock reaches Amazon before you sell out and you don't send more than sells before storage fees climb. Enter last month's sales, your stock at Amazon and on the way, and your lead time: the calculator gives the order date, the quantity, your reorder point and safety stock.
How it's worked out
- Units sold a day = units sold in the last 30 days ÷ 30.
- Stock lasts = (units at Amazon + on the way or ordered) ÷ units sold a day.
- Lead time = production + shipping and receiving: how long after you order the units can be sold.
- Reorder point = units sold a day × (lead time + stock to keep). When stock plus everything on the way falls to it, order.
- Order quantity = units sold a day × the days each order covers. If the order is late, enough to be back at the stock to keep plus those days when it lands.
In the example, 150 units a month is 5 a day. The 600 units at Amazon and on the way last 120 days; with 75 days of lead time and 28 days of stock to keep, the reorder point is 515 units, reached in 17 days. Then order 300 units (60 days of sales, $1,950.00 at $6.50 a unit).
The same product with 200 units at Amazon and nothing on the way lasts 40 days: the order is 63 days late, and even placed today it lands after about 35 days out of stock. The quantity is then 440 units: the stock to keep plus 60 days of sales, with nothing left to count on when it arrives. Out of stock, a listing loses its sales rank and its ads stop, so the cost of those weeks goes on after the stock is back.
The Amazon fees a restock plan runs into
- Too little stock: the low-inventory-level fee can apply to units shipped while a product's days of supply are under 28 days, over both the last 30 and the last 90 days. Keeping 28 days of stock when each order lands keeps you clear of it.
- Too much stock: when your account holds more than 22 weeks of supply, Amazon adds a storage utilization surcharge to every cubic foot; units older than 180 days pay the aged inventory surcharge on top. The FBA storage fee calculator shows what each costs.
- Shipping it in: how you split a shipment changes the inbound placement fee, and the inbound shipping cost guide adds up freight to Amazon.
Restock questions
What is a reorder point?
The stock level at which you place the next order: enough units to keep selling through the lead time and still have your safety stock left when the new units arrive. Count everything already on its way, or you'll order the same units twice.
How much safety stock should an FBA seller keep?
At least 28 days of sales when an order lands, because that's where Amazon's low-inventory-level fee starts. More for products whose sales jump around, whose supplier is often late, or that head into a busy season.
Why use the last 30 days of sales?
It follows recent demand. If the product was out of stock for part of the month, or a busy season is coming, it will sell faster than that: order more.
Can this be done for every product at once?
Yes: MyProfit's Restock page does it for every FBA product every night, from Amazon's stock count, your shipments to Amazon and your supplier invoices, and measures each product's shipping time from the invoices. See it in the sample store.
See when to reorder every product, from your own Amazon data
MyProfit pulls your orders, fees, settlements, returns and ad spend from Amazon every night and shows your real profit by product, day and payout. 30 days of everything free, then $19.99 a month, or keep the free plan: it finds the money Amazon still owes you and checks your FBA fees, for good.