Amazon Inventory Reorder Calculator — Free Stock Planning Tool

How it works

1. Enter your average daily units sold and your supplier lead time.
2. Add your current on-hand and inbound stock.
3. Get your reorder point, days of cover and projected stock-out date instantly.

Pro tips: never stock out, never overstock

1. Order at the reorder point, not when you feel low. Reorder point equals daily sales times lead time plus safety stock days. When available units hit that number, the purchase order goes out - feelings and eyeballing the warehouse do not enter into it. The calculator does this exact math from your own numbers.
2. Set safety stock to 7-14 days normally, 21-30 before Q4. Safety stock is your buffer for demand spikes and shipping delays. A reliable supplier in a stable category needs about a week. A slow boat from overseas ahead of the holiday peak needs a month. Size the buffer to the risk, not to your optimism.
3. The reorder-by date is the real deadline. The tool backs your supplier lead time out of the projected stock-out date to give you the last safe order day. Miss it and your options narrow to air freight - which usually costs more than the margin on the units you are rushing.
4. Count your inbound units. Stock already shipped to Amazon or on the water counts toward your cover, which is exactly why the tool has an inbound field. Ignoring inbound stock is the number-one cause of accidental over-ordering and the storage fees that come with it.
5. Sixty days of cover is a starting point, not a rule. The default target suits steady sellers, but FBA storage fees - especially the fourth-quarter surge - punish overstock hard. If storage costs more than a stockout would, trim the target. If stockouts cost you reviews and rank, pad it. Let the fee math decide.
6. Refresh your daily sales rate monthly. Velocity moves with rank, season, price changes, and reviews. A reorder point built on last quarter's daily rate is fiction dressed as math. Re-run the calculator with fresh numbers every month - it takes a minute and it is the cheapest insurance in the business.
7. Split big orders when lead time is long. Two smaller purchase orders a month apart beat one giant one: less cash tied up, lower FBA storage fees, and the same days of cover. The suggested order quantity is a target for coverage, not a command to buy it all at once.
8. Pad safety stock before known spikes. Prime Day, Black Friday, and your own lightning deals are not normal demand - they are step changes. Temporarily raise safety stock days ahead of events instead of discovering on the morning of the sale that your reorder point assumed an average Tuesday.
9. Watch the trend in days of cover, not just the number. If your days of cover shrink month over month while sales stay flat, your inbound pipeline is leaking - a late supplier, a lost shipment, a PO that never went out. The calculator gives you the number; the trend across runs tells you the story.

Frequently asked questions

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