Calculate reorder points and reorder quantities with lead time demand, safety stock, and inventory level charts over time.
The Reorder Point Calculator turns an average demand rate and supplier lead time into expected lead-time demand, then adds safety stock to identify the inventory level that should trigger replenishment. A reorder quantity can be evaluated alongside that threshold, and the inventory chart shows the resulting drawdown and receipt cycles over time. The frequent mistake is a unit mismatch: daily demand multiplied by lead time stated in weeks does not produce a valid threshold unless one value is converted first.
A concrete input and expected output from the current implementation.
Input
Average demand: 12 units per day Lead time: 5 days Safety stock: 20 units
Expected output
Lead-time demand: 60 units Reorder point: 80 units
Demand during lead time is 12 x 5 = 60 units. Adding 20 units of safety stock gives a reorder point of 80 units.
The calculator first puts demand and lead time on the same time basis. Expected lead-time demand is average demand per period multiplied by the number of periods in the lead time. It then adds safety stock: reorder point = lead-time demand + safety stock. The result is an inventory threshold, not a calendar date or a purchase order.
The chart applies the demand rate across time, marks the reorder threshold, and shows replenishment following the stated lead time. Reorder quantity controls the size of each upward inventory step, while safety stock is the buffer included in the trigger. The pattern helps show whether an assumed quantity would create frequent orders, large inventory peaks, or both.
Yes. Entering zero safety stock makes the reorder point equal expected demand during lead time. The arithmetic is valid, but the result contains no buffer for demand variation, delivery delays, damaged stock, or counting errors. It is therefore most informative when demand and replenishment timing are unusually predictable.
No, not when demand, lead time, and safety stock remain unchanged. Reorder quantity changes how high inventory rises after a receipt and how long it may take to reach the trigger again. The reorder point itself changes only when its demand, lead-time, or safety-stock assumptions change.
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