How to calculate reorder point formula?

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Stock replenishment is an important activity for all retailers. However, there are several things that retailers need to keep in mind while re-stocking their inventory and in this process, calculating the reorder point plays a very important role. 

So what is reorder point, let’s understand that and also learn how to calculate it using a simple reorder point formula. 

What is the reorder point?

“A replenishment/reorder point is the unit quantity on hand that triggers the purchase of a predetermined amount of replenishment inventory.”

Reorder point hence becomes an indicator for the storekeeper to restock the items that are finishing up in the store.  It is similar to the fuel reserve indicator that you have in your motor car or bike so that you can refuel it before you run out of fuel while driving. 

Once the reorder point is hit, the shopkeeper places a new order for the refilling of items so that he can fulfill his future orders successfully without any halt.  

“The end result being no interruption in production and fulfillment activities while minimizing the total quantity of inventory on hand.”

However, one important aspect to keep in mind is that each item/product in the store can have a different reorder point as the reorder point is calculated on the basis of the time taken for your supplier to deliver the products to you. 

This brings us to the next important topic. 

Step-by-Step Guide to Calculating Your Reorder Point

To ensure you always have enough inventory, follow these four key steps to calculate your reorder point:

Step 1: Determine Your Average Daily Usage

Analyze past sales data to calculate the average number of units sold per day.

Step 2: Measure Lead Time

Identify how many days it takes for a supplier to fulfill your order once it is placed.

Step 3: Calculate Safety Stock

Use the safety stock formula to account for demand fluctuations and supplier delays.

Step 4: Apply the Reorder Point Formula

Reorder Point=(Average Daily Usage×Lead Time)+Safety Stock

This calculation ensures stock availability even during unexpected demand surges or supplier delays.

How to calculate reorder point using a formula?

For calculating the reorder point you need a lead time, average daily usage rate, or selling rate of the product and safety stock with the vendor. 

Lead time – is the time taken for the supplier to send the products once the vendor places the purchase order of items. 

Average Daily sold units of the product – meaning on average the number of goods sold on a daily basis. 

Safety stock – is a specific quantity of products kept aside so that they can be used in times of emergency or during stock-outs. 

The formula for calculating reorder point is

Average daily sold units x Lead time 

For instance, Star Mobile Shop sells 25 units of Samsung Smartphones every day and his supplier takes 4 days to send a fresh stock of Samsung Smartphones then what should be the reorder point for Star Mobile shop? 

Therefore, using the above formula:

25 (average rate of daily sold units)   x 4 days (lead time)= 100

The answer is 100 units need to be replenished by the Star Mobile shop from his supplier every 4 days. 

However, in the above example, we are only considering the average number of units sold per day. In reality, this number can increase somedays or decrease some days because we all know that sales are fluctuating every day. So to cover up the sudden rise and fall in the demand for the product a company or shop needs to keep a safety stock. Hence, the reorder point formula can also include safety stock

(Average daily units sold x Delivery Lead time) + Safety stock

Continuing with our example of Star Mobile shop and using this reframed formula, 

(25 x 4) + 25  = 125

Thus, we get the inventory reorder point as 125 units. If Star Mobile Shop’s stock for Samsung Smartphones falls below 125 units, then a new order should be placed. 

Why Safety Stock is Important in Reorder Point Calculations

While the reorder point formula helps determine when to restock, real-world inventory demand is rarely predictable. Sales fluctuate due to seasonal trends, promotions, and unexpected market shifts. Additionally, supplier delays and supply chain disruptions can create gaps in stock availability.

This is why safety stock is crucial—it acts as a buffer inventory to prevent stockouts caused by demand variability and lead time uncertainties.

How to Calculate Safety Stock

The formula for calculating safety stock is:

Safety Stock=(Maximum Daily Usage×Maximum Lead Time)−(Average Daily Usage×Average Lead Time)

Example: Suppose a retailer sells between 20-30 units of a product daily, and supplier delivery takes 3-5 days.

• Maximum Daily Usage = 30 units
• Maximum Lead Time = 5 days
• Average Daily Usage = 25 units
• Average Lead Time = 4 days

(30×5)−(25×4)=150−100=50 units of safety stock

By keeping 50 extra units, the retailer can handle unexpected demand spikes or supplier delays without running out of stock.

Why Reorder Points Matter in Inventory Management

Reorder points play a critical role in inventory management. By ensuring timely replenishment of stock, businesses can:

Avoid Stockouts: Maintain product availability to meet customer demand.
Reduce Excess Inventory Costs: Prevent overstocking and minimize storage expenses.
Enhance Supply Chain Efficiency: Improve supplier coordination and order timing.
Boost Customer Satisfaction: Ensure reliable order fulfillment, reducing lost sales.

Example: A retail store with an optimized reorder point can quickly restock best-selling products, preventing missed sales opportunities and improving customer retention.

Factors That Affect Reorder Point Calculations

Even with an accurate reorder point formula, several external factors influence inventory replenishment:

1. Demand Variability

Sales fluctuate due to seasonal changes, promotions, and unexpected customer trends. Businesses must adjust reorder points dynamically to prevent running out of stock.

2. Lead Time Variability

Supplier delivery times may not always be consistent due to weather delays, supply chain disruptions, or logistics issues. Higher lead time variability requires a larger safety stock buffer.

3. Service Level Targets

The service level target represents the probability of not facing a stockout during the lead time.

• Higher service levels (e.g., 99%) require more safety stock.
• Lower service levels (e.g., 90%) allow for leaner inventory but increase the risk of running out.

Conclusion

Hope the above example has made it clear on how to calculate the reorder point.  

Also, at this point, it is crucial to understand the reorder point only indicates the quantity at which you should place a new order for restocking the item(s). But for knowing how much quantity of a product must be ordered you need to use other methods like Economic Order Quantity method or Just-in-time method.