Reorder Point & Safety Stock Calculator
Find the stock level that tells you to reorder, with enough safety stock to ride out a slow supplier or a busy week.
The formulas
- Reorder point = average daily sales × average lead time + safety stock
- Safety stock, simple method = (most units in a day × longest lead time) − (average daily sales × average lead time)
- Safety stock, service-level method = Z × standard deviation of daily sales × √lead time. Z is 1.28 for 90%, 1.65 for 95%, 1.88 for 97%, 2.05 for 98% and 2.33 for 99%.
The service-level method assumes daily sales vary roughly like a bell curve and lead time is steady. For seasonal products, recalculate before each season. Full walkthrough: reorder points and safety stock explained.
Common questions
What is a reorder point?
The reorder point is the stock level at which you place a new order. It equals the demand you expect during the supplier's lead time, plus safety stock.
What is safety stock?
Safety stock is extra inventory held to cover demand that's higher than average or a delivery that's slower than usual.
Which method should I use?
Use the simple method if you only know your typical and worst-case days. Use the service-level method if you can calculate the standard deviation of daily sales from your sales history.