How to prevent stockouts in your store

A stockout happens when a product a customer wants to buy is no longer available for sale. Depending on how the business is set up, it can affect the shelf, the stockroom or the online store. The way to prevent it is to act on the risk early, before inventory runs out.

The problem doesn't start when inventory hits zero. By then, it's often too late: the sale may be lost, and the customer may switch to another product or go to a competitor.

The right time to deal with a stockout is before it happens.

Why do stockouts happen?

A stockout can have several causes:

Why a fixed threshold isn't always enough

A rule like:

“When 10 units are left, I reorder.”

can work for a product whose sales and supplier lead times are very stable. But ten units don't mean the same thing for every item.

If a product sells ten times a day, those ten units cover about one day of sales. If it sells once every two days, the same ten units last about twenty days.

That's why stock levels always need to be read alongside sales velocity and the time it takes to restock.

Minimum stock, safety stock and reorder point

These three concepts are related, but they don't mean quite the same thing.

Minimum stock

Put simply, minimum stock is the quantity needed to cover sales during the restocking lead time:

Minimum stock = average daily sales × restocking lead time (in days)

For example, if a product sells 5 units a day on average and the supplier delivers within 4 days:

5 × 4 = 20 units

You need about 20 units to cover average demand during the delivery lead time.

Safety stock

Safety stock is an extra buffer that absorbs the unexpected: higher-than-forecast sales, supplier delays or variable delivery times. How much you hold depends on how much uncertainty the business wants to cover.

Reorder point

The reorder point is the stock level at which you should prepare a restock. Put simply:

Reorder point = minimum stock + safety stock

So it's the reorder point, not minimum stock alone, that acts as the practical trigger for restocking. For more on these calculations, read our article on supplier orders and the reorder point.

Metrics that help you predict a stockout

The reorder point is useful, but anticipating stockouts properly usually means combining several pieces of information.

Available inventory

This is the quantity considered available for sale. Depending on your system, this figure may take into account reservations or other movements already recorded.

Sales velocity

This shows how fast an item sells. It's worth looking at recent sales and how they're trending rather than relying only on a long-term historical average.

Stock coverage

Stock coverage estimates how long current inventory will last at the current sales pace. That's why two items with 20 units each can carry very different risks.

Restocking lead time

This is the time between placing the order and the goods actually being available. The longer the lead time, the earlier you need to plan restocking.

Orders already in progress

Low inventory doesn't necessarily mean you need to place a new order: a delivery may already be scheduled. Always factor in quantities already on order before triggering a new restock.

A practical 5-step method to prevent stockouts

A simple approach is to work through these steps:

1. Identify at-risk itemsFind the products whose available inventory is approaching the reorder point or whose coverage is running low.
2. Check sales velocityLook at recent sales and watch for any acceleration. A product can become at risk before it even reaches its usual threshold if demand rises sharply.
3. Check incoming deliveriesBefore ordering, check the quantities already on order and their expected delivery dates.
4. Estimate what you needWork out the quantity needed to cover expected sales until the next restock, including the safety margin you want.
5. Choose the right actionDepending on the situation, you might prepare a supplier order, temporarily increase the order quantity, transfer inventory from another location or keep an eye on the item without acting right away.

This method helps you avoid two opposite mistakes: ordering too late and running out, or ordering too early and ending up with overstock.

High inventory turnover: a signal to watch

Inventory turnover adds another layer of information. An item with rising turnover may simply be selling well. But if remaining inventory is getting low and the supplier lead time is long, that acceleration can also signal an upcoming stockout.

So turnover shouldn't be read on its own. It's more meaningful alongside available inventory, coverage and restocking lead times.

The opposite risk: ordering too early

Preventing stockouts doesn't mean keeping inventory high across the board. An overly cautious policy just moves the problem and creates overstock.

The goal is balance: enough inventory to cover demand and reasonable uncertainty, but no more than you need.

That's why restocking levels should be adjusted to the sales, lead times and actual behavior of each item.

How can AI help you anticipate stockouts?

With hundreds or thousands of items, monitoring every stock level by hand quickly becomes unmanageable. An AI agent connected to the business's data can make this analysis easier.

Instead of asking:

“Which products are out of stock?”

the store owner can look ahead:

“Which items are at risk of running out this week?”

The analysis can then combine the available data: remaining inventory, recent sales, supplier lead times and orders in progress. The store owner can follow up with:

“Which of them have no delivery scheduled?”

Then:

“Prepare a restock for those items.”

The value is in shifting from discovering a stockout after the fact to identifying the items that need action before inventory hits zero.

How do you determine how much to reorder?

Spotting the risk isn't enough. The reorder point tells you when to restock, but not how much to order.

The order quantity can depend on:

• available inventory;
• expected sales;
• orders already in progress;
• the safety stock you want;
• the supplier lead time;
• pack sizes;
• minimum order quantities;
• the target stock level.

A supplier order should therefore be based on actual needs and supply constraints. For more on this, read our article on supplier orders and demand forecasting.

Preventing stockouts across multiple stores

For a business with several locations, a new supplier order isn't always the best answer. Say one store is about to run out of an item while another location has several weeks' worth of the same product. A transfer can rebalance stock across locations without increasing overall inventory.

Before recommending an order, it's worth checking:

• the inventory available at the other locations;
• their sales velocity;
• their stock coverage;
• how long the transfer would take.

A transfer isn't always the better option: you also need to weigh its cost, its lead time and the needs of the store sending the stock.

From analysis to restocking with Gillia

With Gillia's inventory management, store owners can query their data to find the items that need attention. For example:

“Which items are at risk of running out this week?”

Then:

“Prepare a restock for the at-risk items.”

Depending on the data available, Gillia can pull together the relevant information and prepare the corresponding operation for your approval.

For multi-store businesses, the analysis can also reveal that another location has excess inventory. The transfer itself is still a separate operation, created from inventory management.

To see how this fits into the full inventory cycle, read our guide to store inventory management. You can also explore Gillia use cases for tracking stockouts and items below their reorder threshold.

Anticipate stockouts instead of reacting to them

Good stockout management doesn't mean reacting when inventory hits zero. It means spotting, early enough, the items whose remaining stock may not cover demand until the next delivery.

That requires combining several data points: available inventory, sales, coverage, lead times, orders in progress and safety stock.

The more reliable and up to date this data is, the better the business can step in at the right time, without trading stockout risk for excess inventory.

To learn more, explore Gillia inventory management: real-time tracking, stock entry from a photo and alerts before you run out.