Inventory Reorder Calculator
Find the stock level that should trigger a new purchase by combining daily sales, supplier lead time and safety stock.
Recent
Formula
How the calculation works
The calculator multiplies average daily sales by the supplier lead time in days to cover demand while waiting for delivery.
Safety stock is then added on top so a sudden sales spike or a late delivery does not cause a stockout.
The current stock is compared with that reorder point, and any shortfall is reported as the quantity to buy.
Common mistakes
- Setting safety stock to zero, which leaves no cushion when sales rise unexpectedly or the supplier is late.
- Using the best sales day instead of the average daily sales, which inflates the reorder point and ties up cash in excess stock.
When to use it
- Shop owners and online sellers use it to know when to place the next order before stock runs out.
- It also shows how many units are short at the current stock level so a purchase quantity can be planned.
Worked example
With average daily sales of 20 units, a lead time of 7 days and safety stock of 50 units, the reorder point is 190 units, and with 100 units in stock the shortfall is 90 units.
Common questions
How do I choose the safety stock figure?
Safety stock should cover demand during any delay or sudden rise in sales, so many shops set it to a few days of average sales, for example five to ten days.
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