Reorder point and safety stock calculator for Amazon FBA sellers
Run out at the fulfilment centre and sales stop until the next shipment is checked in. Send too much and it sits paying storage. Enter one SKU's daily sales and lead time to get its reorder point, safety stock and how many units to send. Nothing leaves your browser.
Selling on Amazon.com? Use the US version.
Reorder in about 6.8 days, when stock falls to 319 units.
Your numbers
- Reorder point
- 319 units
- Safety stock
- 67 units
- Lead-time demand
- 252 units
- Days of cover now
- 33.3 days
- Order quantity
- 279 units
- Reorder in
- 6.8 days
Reorder in about 6.8 days, when stock falls to 319 units.
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The formulas
- Reorder point = average daily units × lead time (days) + safety stock.
- Safety stock, statistical = z × √(L × σd² + d² × σL²), where d is average daily units, L the average lead time, σd and σL their standard deviations, and z comes from the service level (95% → 1.645).
- Safety stock, quick = (highest daily units × longest lead time) − (average daily units × average lead time).
- Order quantity = d × (L + cover days) + safety stock − (on hand + inbound).
Results are rounded up to whole units. They are estimates — seasonality, promotions and stock limits at the FC still need your judgement.
Reorder questions sellers ask
What is a reorder point?
The stock level at which you place the next order, so the new stock arrives before you run out. It is the demand you expect during the lead time (average daily units × lead-time days) plus safety stock.
What is safety stock?
Extra units that cover busier-than-usual days and late shipments. The statistical method uses z × √(lead time × daily-sales variance + daily sales² × lead-time variance); the quick method uses (highest daily sales × longest lead time) − (average daily sales × average lead time).
What lead time should an FBA seller use?
The whole time from placing the order to units being sellable at the fulfilment centre: supplier production, transit to the FC and the FC's inbound check-in. Use your own history — it differs by supplier, route and FC.
Which service level should I pick?
Higher service levels mean fewer stock-outs but more units held, and stored stock costs storage fees. Pick a higher level for the SKUs where a stock-out hurts most. It is a trade-off, not a rule.
How is the order quantity worked out?
Order-up-to level = average daily units × (lead time + the days you want the order to cover) + safety stock. The order quantity is that level minus the units you already have on hand and inbound, never below zero.
Related free tools
- Reorder-point calculator for Amazon US sellers — the same maths with a US example.
- Amazon.in settlement profit calculator
- Amazon FC GST / APOB guides — before stock goes to a new FC, the FC must be on a GST registration for its state.
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