Inventory planning
Lead Time Demand
By the Supply Chain Manager team · Updated October 16, 2026
Lead time demand is the quantity you expect to sell while waiting for a replenishment order to arrive: average daily demand multiplied by lead time.
It is the first half of the reorder point. If stock on hand when you order is less than lead time demand, you will run out before the delivery lands, even if the supplier is perfectly on time.
Lead time demand is an average. In practice, demand during the lead time varies from cycle to cycle, and the lead time itself varies too. That is why the reorder point adds safety stock on top: lead time demand covers the expected case, and safety stock covers the cycles where demand runs higher or the supplier runs late.
How to calculate lead time demand
Lead Time Demand = Average Daily Demand × Lead Time (days)
Lead time demand example
Illustrative numbers: 21 units a day and an 8-day lead time give lead time demand of 168 units. Add a safety buffer and you get the reorder point.
Why lead time demand matters for distributors
It makes the cost of long lead times visible. Doubling lead time doubles the stock you must hold just to bridge the wait, before any buffer for uncertainty.
Common lead time demand mistakes
- Multiplying monthly demand by a lead time in days without converting the units.
- Forgetting that demand during the lead time varies, which is what safety stock is for.
Examples on this page use made-up round numbers to show the calculation. They are not benchmarks or results from real businesses.