Lead Time & Reorder Point Calculator
Calculate total manufacturing and supply chain lead time, lead time demand, and optimal inventory reorder point (ROP).
How to Use the Lead Time & Reorder Point Calculator
In supply chain management and lean manufacturing, total lead time measures the total calendar latency from the moment a replenishment order is initiated until the inventory is received, inspected, and available for sale in your warehouse. Breaking lead time into order preparation, factory production, and freight transit exposes bottlenecks that tie up working capital.
Formula and Calculation Methodology
- T_prep: Internal purchase order approval and supplier queue handling days
- T_production: Factory manufacturing, assembly, and quality inspection days
- T_transit: Shipping, port handling, customs clearance, and warehouse receiving days
- ROP: Reorder Point in units required to prevent stockouts
Accurate lead time calculation is the cornerstone of your Reorder Point (ROP) formula. By multiplying your total lead time in days by your average daily unit sales—and adding a safety stock buffer for demand spikes or shipping delays—you establish the exact inventory threshold at which a new purchase order must be triggered to avoid costly stockouts.
Typical Supply Chain Lead Time Benchmarks by Sourcing Method
| Sourcing Channel | Prep & Queue | Production | Transit & Receiving | Total Lead Time |
|---|---|---|---|---|
| Domestic WholesaleStock | 1 – 2 days | 0 days (In stock) | 2 – 5 days | 3 – 7 days |
| Domestic Custom Mfg | 2 – 3 days | 10 – 15 days | 3 – 5 days | 15 – 23 days |
| Overseas Air Freight | 2 – 4 days | 15 – 25 days | 5 – 8 days | 22 – 37 days |
| Overseas Ocean Freight | 3 – 5 days | 20 – 30 days | 28 – 42 days | 51 – 77 days |
Frequently Asked Questions
What is the difference between manufacturing lead time and customer lead time?
Manufacturing lead time includes raw material procurement and factory production, whereas customer (order-to-delivery) lead time is the time from when a customer places an order until it arrives at their door.
Why do I need safety stock in my lead time calculation?
Even if your average lead time is 19 days, supplier delays or unexpected sales surges can deplete inventory early. Safety stock acts as an insurance buffer against variance.
How does reducing lead time lower inventory costs?
Shorter lead times reduce Lead Time Demand, allowing you to hold smaller cycle stock and lower safety stock while maintaining the same service level.