Definition
A reorder point (ROP) is the inventory level at which a new purchase order must be placed to replenish stock before it runs out. It accounts for both the lead time required to receive new inventory and the safety stock needed to absorb variability in supply and demand. When on-hand inventory drops to the reorder point, a replenishment order is triggered automatically or manually.
Understanding Reorder Point (ROP)
The reorder point is the operational trigger that connects inventory visibility to procurement action. Without it, companies rely on gut feel or periodic manual checks to decide when to order. With it, replenishment becomes systematic and predictable.
The core logic is straightforward: if it takes 10 days to receive a new order and average daily demand is 100 units, the company must reorder when it still has at least 1,000 units on hand. Any lower and there is a risk of running out before the new order arrives.
Modern inventory management systems automate reorder point calculations and trigger purchase orders without manual intervention. This reduces the operational burden on procurement teams and eliminates the human error that causes both stockouts and overstock.
Core Reorder Point Components
- Average Daily Demand: The typical number of units sold or used per day. Calculated from historical sales data over a representative period.
- Lead Time: The total time from placing a purchase order to receiving the inventory. Includes supplier processing time, transit time, and receiving time.
- Safety Stock: Reserve inventory held above expected demand to absorb variability. Added to the reorder point to protect against demand spikes or delayed deliveries.
Reorder Point Formula
ROP = (Average Daily Demand x Lead Time) + Safety Stock
Example: A company sells 50 units per day on average. Supplier lead time is 8 days. Safety stock is 100 units.
ROP = (50 x 8) + 100 = 500 units
When inventory drops to 500 units, a new purchase order is placed. By the time it arrives 8 days later, the company will have consumed approximately 400 units, leaving the 100-unit safety stock intact.
Related Concepts
- Safety Stock : Reserve inventory that protects against variability in supply and demand. A key input to the ROP calculation.
- Lead Time: The time from order placement to receipt. Directly determines how much inventory must be on hand when reordering.
- Demand Planning: The process of forecasting future demand. More accurate forecasts enable tighter ROP settings with less safety stock.
- Inventory Turnover Ratio: How efficiently inventory is cycled. ROP affects how often orders are placed and how much inventory is held at any time.
