📦Reorder Point Calculator

About this tool

Enter your average daily demand and how much it varies, the supplier's average lead time and how much that varies, and the service level you want. The calculator shows the reorder point, the demand expected during the lead time, the safety stock and, from your current stock, whether to order now or how many days remain. If you already use a fixed safety stock, enter it instead.

How the reorder point is set

The reorder point is the stock level that triggers the next order: average daily demand × lead time, plus safety stock. Safety stock covers the days when demand runs high or the supplier is late. Here it is z × √(lead time × demand variance + daily demand² × lead-time variance), where z comes from the service level, the chance of not running out during one replenishment cycle. Selling 40 units a day, with a standard deviation of 8, from a supplier who takes 12 days give or take 2, needs about 140 units of safety stock at a 95% service level. The reorder point is then about 620 units. Raising the target to 99% lifts safety stock to about 197 units, roughly 40% more, which is the trade-off between stock-outs and cash tied up in inventory. Honest limits: the formula assumes fairly steady, roughly normal demand, so seasonal or promotional items need a forecast. The EOQ calculator sets how much to order, the inventory turnover calculator measures the result and the purchase order generator writes the order. Standard deviation explained: what it measures, how it's calculated, and the 68–95–99.7 rule explains the variability inputs.

Frequently asked questions