Lead Time Demand Calculator
Units you will sell while waiting for a delivery.
Approval, ordering, receiving and putaway — suppliers quote only their part.
Lead time demand
315
over 21 total days
Real lead time runs from the decision to order to stock being sellable. Using the supplier's quoted figure alone is a common source of stockouts.
How the Lead Time Demand Calculator works
Lead time demand is the quantity you will sell while an order is in transit. It is the core of the reorder point, and it is where most stockouts originate — not from bad forecasting overall, but from underestimating this specific window.
Not financial advice. Marketplace fees change, and they vary by country, plan and seller status. Every rate here is an editable default, not a quoted price — check the platform's current fee schedule before you price a product against it. This is not tax or business advice.
Frequently asked questions
How is lead time demand calculated?
Average daily demand × lead time in days. Selling 15 units a day against a 21-day lead time means 315 units will go out before the replacement arrives.
Should lead time include my own processing?
Yes. Real lead time runs from the moment you decide to order to the moment stock is sellable — your approval time, the supplier's production, transit, customs, receiving and putaway. Suppliers quote only their own portion.
How do I handle variable lead times?
Use the average here and cover the variability with safety stock. If lead time swings widely, calculate against a longer percentile — planning to the 90th percentile rather than the mean is common where late delivery is costly.
Why do stockouts happen despite a reorder point?
Usually because demand spiked during the lead time window, or the lead time itself stretched. Both are variability rather than forecast error, and both are what safety stock exists to absorb.