About this tool
Reorder Point & Safety Stock Calculator is a free, in-browser tool that tells you when to place a replenishment order so you do not stock out during the lead time. Enter your average daily usage, the lead time in days, an optional demand standard deviation, and a service level, and it returns the reorder point, safety stock, lead-time demand and the Z-value used. Nothing is uploaded.
Safety stock = Z × σ × √(lead time), where σ is the daily demand standard deviation and Z is the service-level factor (90% → 1.28, 95% → 1.645, 97.5% → 1.96, 99% → 2.33). The reorder point = average daily usage × lead time + safety stock, so it covers expected demand across the lead time plus a buffer sized to your chosen service level. Leave σ blank and safety stock is zero, giving the simple usage × lead-time reorder point.
Use it to set min levels in an inventory system: a higher service level or more variable demand raises the safety-stock buffer, protecting against stockouts at the cost of holding more inventory.