Reorder Point Calculator

It is the on-hand quantity that tells the replenishment system "order more now." When inventory falls to the reorder point, a purchase order fires. Set the number correctly and the next delivery arrives just as the shelf runs low. Set it wrong and you either lose the sale or park working capital in overstock.

Use historical demand variability and a target service level. The Safety Stock Calculator runs the statistical Z-score formula in the browser, and the Safety Stock Calculation Guide walks through both the simple max-average formula and the statistical version. For batch calculations across multiple SKUs, download the Safety Stock Calculator (Excel) template.

Yes. Use the observed lead time from the last 8 to 12 orders, not the number your supplier quotes. Supplier-quoted lead time is a target. Observed lead time is what your reorder point actually needs. Real lead time typically runs 30 to 50 percent longer than what suppliers quote once you include PO processing, transit variability, customs clearance, receiving and put-away.

Quarterly at minimum. Monthly for fast-moving or seasonal SKUs. Any category with lead-time volatility (offshore sourcing, consolidated freight, contract manufacturing) deserves a review after each quarter-end supplier scorecard. Static ROPs are the single biggest source of preventable stockouts across a stable assortment.

Reorder point tells you WHEN to order. EOQ tells you HOW MUCH to order in each PO. They work together. EOQ sizes the order quantity that balances holding cost against ordering cost. Reorder point sets the trigger. Missing either half creates a broken replenishment policy. The EOQ Formula Guide covers where the two connect.

Four show up repeatedly. Using supplier-quoted lead time instead of observed lead time. Forgetting to recompute ROP when demand shifts seasonally or during a promotion. Applying the same safety stock across every SKU regardless of ABC class. And setting ROP once at go-live and never reviewing it. The Reorder Point Formula Guide covers each with a concrete fix.

A-class SKUs typically get higher safety stock and a higher target service level (95 to 99 percent), which pushes their ROP up. C-class SKUs run leaner (85 to 90 percent service). Applying one blanket ROP formula across the assortment wastes cash on the tail and starves the head. Use the ABC Analysis Calculator to classify your assortment first, then set service levels and safety stock by class.

No. A higher ROP means more cash on the shelf and more markdown risk on slow items. The right ROP is the smallest number that keeps service level at the target. If inventory turnover is dropping across a category and stockouts are not, the reorder points are almost certainly too high. If DIO is above the category benchmark by 10+ days, ROP rightsizing is one of the first three levers to check.

Continuous review checks on-hand against ROP after every sale and fires a PO the moment ROP is crossed. Modern POS/ERP systems handle this by default and give the tightest control. Periodic review checks inventory at fixed intervals (weekly, biweekly) and reorders anything below ROP at that time. Periodic review is simpler but requires higher safety stock to cover the review interval on top of the lead time, which typically pushes ROP up by 15 to 25 percent. Continuous is the default recommendation for any assortment where modern replenishment tooling exists.

Under vendor-managed inventory, the supplier owns the ROP calculation and the replenishment decision, not the retailer. The retailer shares POS or on-hand data via EDI, and the supplier fires shipments against ROPs the supplier maintains. The math is identical, but the responsibility shifts. VMI programs typically produce 15 to 20 day DIO improvements as a side effect, because suppliers who see downstream demand data tend to set tighter, more accurate ROPs than the retailer would set from the demand-side alone.