Estimate a basic safety-stock buffer from average and maximum daily usage plus average and maximum supplier lead time.
Safety stock formula used
This calculator uses the basic maximum-versus-average planning method:
It also shows a simple reorder-point estimate: average demand during average lead time + safety stock.
Worked example
If maximum daily usage is 40 units, maximum lead time is 12 days, average daily usage is 25 units and average lead time is 8 days, the estimated safety stock is 280 units.
This is a basic inventory-planning method, not a universal service-level or statistical safety-stock model. Seasonal demand, supplier variability, service-level targets, carrying cost and forecast error can justify a different method.
References: Shopify min-max inventory guide and NetSuite stockout guidance.