Replenishment Lead Time Calculator
Replenishment Lead Time Calculator
What Is Replenishment Lead Time?
Replenishment lead time is the total elapsed time from when a reorder is triggered to when the inventory is available for use. It encompasses three components: supplier lead time (time for the vendor to ship the goods), internal processing time (purchase order creation, approval, and receipt), and inspection time (quality control before goods enter usable inventory). Understanding total replenishment lead time is foundational to setting accurate reorder points and avoiding stockouts.
How the Formulas Work
Total Replenishment Lead Time = Supplier Lead Time + Internal Processing Time + Inspection Time. Safety Stock = Safety Days × Average Daily Demand — this buffer absorbs demand spikes and supplier delays. Reorder Point (ROP) = (Average Daily Demand × Total Lead Time) + Safety Stock — place a new order when inventory falls to this level. Economic Order Quantity (EOQ) = √(2 × Annual Demand × Order Cost ÷ Holding Cost per Unit) — EOQ minimizes the combined cost of ordering and holding inventory, derived from Wilson's formula (1913), still the industry standard.
Understanding Your Results
The primary result shows total lead time in days — this is how far in advance you must trigger replenishment. The reorder point tells you the exact inventory level at which to place a new order. Safety stock is a permanent buffer held to cover variability. The EOQ (unlocked in Advanced Options) shows the mathematically optimal order quantity to minimize total inventory costs. The bar chart breaks down each lead time component, helping you identify where delays are concentrated and where process improvements would have the greatest impact.
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