How to Know When to Reorder Inventory for Your Online Store

Running out of stock is expensive.

But overstocking is also expensive.

That is why inventory control is one of the most important parts of running a product-based business. If you reorder too late, you lose sales. If you reorder too early, you trap cash in inventory that may not move quickly.

The goal is not to guess. The goal is to know when to reorder based on actual usage, lead time, and safety stock.

Here is how to build a smarter reorder system for your online store.

Why Reorder Timing Matters

Poor reorder timing can create several problems:

• Stockouts
• Delayed customer orders
• Emergency supplier orders
• Higher shipping costs
• Overstock
• Dead stock
• Cash flow problems
• Poor customer experience

Many small e-commerce businesses reorder based on instinct. They wait until stock “looks low” or until a product sells out.

That approach works only when the business is small. As sales grow, guessing becomes dangerous.

A better system uses reorder points.

What Is a Reorder Point?

A reorder point is the stock level where you should place a new order before you run out.

In simple terms:

Reorder Point = Demand During Lead Time + Safety Stock

This means you need to know:

• How many units you sell or use per day
• How long the supplier takes to deliver
• How much backup stock you want to hold

Once your stock drops to the reorder point, it is time to replenish.

Step 1: Know Your Daily Usage Rate

Your daily usage rate is how many units you sell or use per day on average.

For example:

If you sell 300 units in 30 days:

300 ÷ 30 = 10 units per day

That means your daily usage rate is 10 units.

You should calculate this for each product, not your entire store as one number. Different products move at different speeds.

Step 2: Know Your Supplier Lead Time

Lead time is how long it takes to receive inventory after you place an order.

For example:

If you order from your supplier on Monday and receive the stock the following Monday, your lead time is 7 days.

Lead time should include:

• Supplier processing time
• Production time if applicable
• Shipping time
• Customs delay if importing
• Receiving and restocking time

Do not use the supplier’s best-case estimate only. Use the average real lead time based on your experience.

Step 3: Calculate Demand During Lead Time

Demand during lead time tells you how much stock you expect to sell while waiting for new inventory.

Formula:

Daily Usage Rate × Lead Time = Demand During Lead Time

Example:

• Daily usage rate: 10 units
• Lead time: 7 days

10 × 7 = 70 units

That means you expect to sell 70 units while waiting for the next order to arrive.

Step 4: Add Safety Stock

Safety stock is extra inventory kept as a buffer against delays or unexpected demand.

You need safety stock because things go wrong:

• Supplier ships late
• Demand spikes
• Courier delays occur
• Stock arrives damaged
• Customs delays happen
• Sales increase unexpectedly

A simple method is to add 20% to 30% extra stock as a buffer.

Example:

If demand during lead time is 70 units, 20% safety stock would be:

70 × 20% = 14 units

So your reorder point becomes:

70 + 14 = 84 units

That means when stock reaches 84 units, you should reorder.

Step 5: Watch Fast-Moving SKUs More Closely

Not every product needs the same level of attention.

Your highest-priority products are usually the ones with:

• High sales volume
• High profit margin
• Fast turnover
• Long supplier lead time
• Strong customer demand

These products should be monitored more often because a stockout can hurt revenue quickly.

This is where SKU prioritization helps. Classify products into A, B, and C categories:

A items: highest priority
B items: moderate priority
C items: lower priority

Focus your best inventory control on A items first.

Step 6: Avoid Overstocking Slow Movers

Stockouts are not the only inventory problem. Overstock can be just as damaging.

Overstock ties up money that could be used for:

• Marketing
• Better suppliers
• Faster shipping
• New products
• Packaging improvements
• Cash reserves

If a product has not sold in 60 to 90 days, it may be dead stock or slow-moving inventory.

For slow movers, consider:

• Bundling
• Discounts
• Limited-time offers
• Removing from future purchase orders
• Replacing with faster-moving products

The goal is to keep money moving, not trapped on shelves.

Step 7: Use an Inventory Tracker

Trying to manage reorder points manually becomes messy fast.

A good inventory tracker should help you monitor:

• Current stock
• Daily usage
• Weekly usage
• Monthly usage
• Lead time
• Safety stock
• Reorder point
• Reorder status
• Inventory value

The most important part is the reorder status. You want the system to show clearly when a product needs to be restocked.

Even a simple spreadsheet can make a major difference if it is structured properly.

Step 8: Review Inventory Weekly

Inventory should not be reviewed only when something goes wrong.

Create a weekly inventory check.

Look at:

• Products below reorder point
• Products close to reorder point
• Overstocked products
• Dead stock
• Fast-moving products
• Supplier delays
• Inventory value

This keeps you ahead of problems instead of reacting after stock runs out.

Common Inventory Mistakes to Avoid

Avoid these mistakes:

• Reordering based on emotion
• Ignoring supplier delays
• Treating all SKUs equally
• Failing to track daily usage
• Overstocking slow sellers
• Forgetting safety stock
• Waiting until products sell out
• Not reviewing inventory weekly

These mistakes are common, but they are fixable with the right system.

What This Means for Your Business

Knowing when to reorder inventory is one of the simplest ways to protect sales and cash flow.

You do not need a complicated warehouse system to start. You need to track the right numbers:

• Daily usage
• Lead time
• Safety stock
• Reorder point
• Stock status

Once those are visible, inventory decisions become much easier.

If your store keeps running out of stock or holding too much inventory, the issue is not just inventory. It is a system problem.

Fix the system, and the business becomes easier to control.

 

Want a ready-made system for this?

The 7-Day Logistics Fix includes an inventory tracker, SKU prioritization tool, KPI dashboard, fulfillment cost estimator, SOP template, supplier negotiation script, and a step-by-step logistics guide.

Get the 7-Day System →