How to Calculate Reorder Points with the ROP Formula

October 17, 2023

Managing inventory is an essential aspect of many businesses, and knowing when to reorder stock can make the difference between a seamless operation and costly interruptions. One of the critical components of inventory management is determining the reorder point (ROP). The reorder point ensures that new stock is ordered in time to replenish supplies before they run out. In this article, we’ll delve into how to calculate the reorder point using the ROP formula.

What is the Reorder Point (ROP)?

The reorder point (ROP) is the level of inventory which triggers an action to replenish that particular inventory stock. It is a minimum quantity that a company holds in stock, and once inventory falls below this amount, the next order is placed.

The ROP Formula

The basic formula to calculate the reorder point is:

ROP = Lead Time Demand

Lead Time Demand is the product’s average demand or sales per day multiplied by the lead time in days.

In more uncertain environments, where demand and lead time vary, a more comprehensive formula can be used:

ROP = (Average Daily Demand × Average Lead Time) + Safety Stock

Average Daily Demand is the average number of units sold per day.
Average Lead Time is the average time it takes for an order to arrive once it’s placed.
Safety Stock is additional inventory held to guard against variability in demand or lead time.

Steps to Calculate ROP

1. Determine Average Daily Demand: This can be calculated by analyzing past sales data. For instance, if you sold 300 units over 30 days, the average daily demand is 10 units/day.

2. Determine Average Lead Time: This is the time it takes from when an order is placed until it’s received. If you’ve historically experienced lead times ranging from 5 to 7 days, your average might be 6 days.

3. Calculate Safety Stock (if needed): Safety stock is a buffer against sudden increases in demand or delays in lead time. Determining the appropriate amount of safety stock requires a more in-depth analysis, considering factors like desired service levels and the standard deviations of demand and lead time.

4. Apply the ROP Formula: Use the formulas mentioned above to compute your reorder point.


Let’s say a retail store has the following data for a particular product:
Average Daily Demand: 10 units
Average Lead Time: 6 days
Safety Stock: 15 units
Using the formula, the ROP would be:

ROP = (10 × 6) + 15
ROP = 60 + 15
ROP = 75

In this case, when the inventory level for this product drops to 75 units, it would be time to reorder.

Benefits of Accurately Calculating ROP

Reduces Stockouts: Accurate ROP calculations can significantly decrease the chances of running out of stock.

Minimizes Excess Inventory: Avoiding over-ordering saves storage costs and reduces the risk of obsolescence.

Enhances Cash Flow Management: By efficiently managing inventory, businesses can better allocate resources and capital.


The reorder point (ROP) is a fundamental metric in inventory management that helps businesses ensure product availability while optimizing inventory levels. Understanding how to accurately compute it using the ROP formula can greatly aid in making informed decisions, resulting in improved operational efficiency and customer satisfaction.

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