Stockouts can look like a simple inventory problem, but they usually affect much more than the stock count. A product is unavailable. A customer cannot place an order. A team may have to delay fulfillment, contact buyers, split shipments, or rush a supplier order. What started as “we ran out” can quickly turn into lost sales, extra work, and a weaker customer experience.
For growing eCommerce businesses, stockouts are not always caused by one big mistake. They often happen when sales move faster than expected, supplier orders arrive late, inventory counts are inaccurate, or teams do not have a clear replenishment process in place.
The good news is that many stockouts can be reduced with better planning. Forecasting, reorder points, safety stock, supplier purchase orders, and accurate inventory data all help teams restock before inventory becomes critical.
This guide explains what stockouts are, why they happen, and how eCommerce businesses can prevent them with a more connected inventory workflow.
What Is a Stockout?
A stockout happens when a product is unavailable for sale or fulfillment because there is not enough inventory to meet demand.
In eCommerce, a stockout may mean a product page shows as out of stock, an order cannot be fulfilled, or a team has to wait for more inventory before shipping. It can happen with finished goods, components, bundled products, or supplies needed to prepare orders.
Stockouts are especially frustrating because they often show up at the worst time. A product starts selling well, a promotion performs better than expected, or a busy season creates more demand than usual. Then the business realizes inventory will not last until the next supplier order arrives.
Preventing stockouts starts with understanding what causes them.
Why Stockouts Happen
Stockouts can happen for several reasons. Sometimes demand changes quickly. Supplier timelines shift. Sometimes inventory looks available in one system but is already committed to orders somewhere else.
Common causes include:
- Inaccurate inventory counts: If available inventory is wrong, teams may think there is more stock than there really is.
- Unexpected demand spikes: Promotions, holidays, viral products, or wholesale orders can move inventory faster than planned.
- Long or changing supplier lead times: If replenishment takes longer than expected, inventory may run out before the next shipment arrives.
- No clear reorder point: Without a defined restocking trigger, teams may wait too long to place supplier orders.
- Too little safety stock: Without a cushion, there may not be enough backup inventory for delays or demand changes.
- Disconnected sales channels: Products selling across multiple channels can create inventory conflicts if stock is not updated quickly.
- Poor visibility into purchase orders: Teams may not know what has already been ordered, what is inbound, or when inventory is expected to arrive.
For many eCommerce businesses, stockouts happen when these issues overlap. A product sells faster than expected, the supplier takes longer than usual, and the team does not catch the problem until inventory is already too low.
Why Stockouts Matter for eCommerce Businesses
Stockouts do more than interrupt sales. They can affect the entire order workflow. When a product is unavailable, customers may leave the site, buy from a competitor, or lose confidence in the business. If an order has already been placed, the team may need to delay fulfillment, issue a refund, contact the customer, or split the shipment.
Stockouts can also create internal pressure. Purchasing teams may have to rush supplier orders. Warehouse teams may have to work around missing inventory. Support teams may have to explain delays. Marketing teams may have to pause campaigns for products that cannot be fulfilled.
That is why stockout prevention is about more than keeping shelves full. It is about protecting the customer experience and keeping orders moving.
Stockouts are easier to manage when they are part of a broader eCommerce inventory management process. Inventory data, purchasing, fulfillment, and sales channels all need to work together.
How to Prevent Stockouts
Preventing stockouts starts with better visibility. Your team needs to know what is available, what is selling, what has already been committed to orders, what is on the way, and when more inventory is expected to arrive. From there, the process becomes easier to manage.
Keep Inventory Counts Accurate
Accurate inventory counts are the foundation of stockout prevention. If the numbers are wrong, every decision built on those numbers becomes harder to trust. A product may look safe when it is already running low. Another product may look unavailable when there is still stock in the warehouse. Either way, the team loses time trying to confirm what is actually true.
Inventory accuracy becomes more important as order volume grows. Products may be selling across multiple channels, sitting in different locations, or already committed to open orders. Your team needs a clear view of what is actually available before making replenishment decisions.
Use Inventory Forecasting to Plan Ahead
Inventory forecasting helps eCommerce businesses estimate future demand before inventory problems happen. A good forecast looks at sales history, current stock, supplier lead times, seasonal patterns, and upcoming changes like promotions or busy periods. It helps your team see which products may need attention soon, instead of waiting until they are already close to running out.
Forecasting does not mean predicting demand perfectly. It gives your team a better way to plan what to buy next based on the information available.
For example, if a product usually sells faster before the holidays, your team can plan supplier orders earlier. If a product is slowing down, you may decide not to reorder as much. If a promotion is coming up, the forecast can help you prepare for the extra demand.
For more context, read our guide to inventory forecasting for eCommerce.
Set Reorder Points for Key Products
A reorder point is the inventory level that tells your team when it is time to order more of a product. This helps prevent stockouts because the team is not waiting until inventory feels low. Instead, each product has a defined restocking trigger based on sales velocity, supplier lead time, and safety stock.
For example, if a product sells 5 units per day and the supplier takes 10 days to deliver, your team needs enough inventory to keep selling during that 10-day window. If you also keep extra inventory as a cushion, that amount should be included in the reorder point. Reorder points are especially useful for best sellers, seasonal products, long-lead-time items, and products that are expensive to run out of.
For a deeper look at the formula, read our guide on how to calculate reorder points.
Keep Enough Safety Stock
Safety stock is extra inventory kept on hand to reduce the risk of running out. It gives your team a cushion when demand is higher than expected, a supplier runs late, inventory counts are slightly off, or a promotion creates more orders than usual.
The goal is not to overbuy every product. The goal is to keep backup inventory for the products where a stockout would create bigger problems. A best seller may need more of a cushion than a slow-moving SKU. A product with an unreliable supplier may need more backup inventory than one that can be replenished quickly.
Safety stock works best when it is reviewed regularly. Sales patterns, supplier timelines, and customer demand can all change over time.
For more on this topic, read our guide: Safety Stock Explained: How Much Extra Inventory Should You Keep?
Track Supplier Purchase Orders
Purchase orders play a major role in stockout prevention because they show what inventory is already on the way. Once a product needs to be reordered, the supplier PO creates a record of what was ordered, how many units were requested, when the order was placed, and when inventory is expected to arrive.
Without clear PO tracking, teams may not know whether a supplier order was placed, whether it was confirmed, or whether the delivery date changed. That can lead to duplicate orders, missed replenishment, or surprises when inventory does not arrive on time.
Supplier purchase orders also help your team avoid reacting to inventory counts alone. A product may look low today, but a shipment may already be arriving next week. Or the opposite may be true: the product may look fine today, but no replacement inventory has been ordered yet.
For more on this process, read our guide to purchase orders for eCommerce. Teams using Ordoro can also learn how to create and manage purchase orders in Ordoro.
Watch Sales Channels and Fulfillment Together
Stockouts can become harder to prevent when products sell across multiple channels. A SKU may be available in one place, committed to orders in another, and still showing as sellable somewhere else. If inventory updates do not move quickly across channels, teams may oversell products without realizing it.
This is where inventory connects directly to fulfillment. Your team needs to know not only what is on the shelf, but what is already promised to customers. Available inventory should account for open orders, committed stock, and incoming replenishment.
That visibility helps teams make better decisions before a stockout affects the customer.
When Spreadsheets Make Stockout Prevention Harder
Spreadsheets can help small teams manage inventory in the beginning. They are flexible, familiar, and easy to update manually. But stockout prevention depends on current information.
If sales data, supplier lead times, inventory counts, and purchase orders live in different places, the team may not see the full picture until it is too late. A spreadsheet may show stock on hand, but not what is already committed to open orders. A supplier order may be tracked in email. A reorder point may be buried in another file.
The more places your team has to check, the easier it is to miss the signal that inventory needs attention.
For more on this stage of growth, read our guide to 7 signs you’ve outgrown spreadsheet inventory management.
How Inventory Management Software Helps Prevent Stockouts
Inventory management software helps eCommerce businesses prevent stockouts by connecting the information teams need to make replenishment decisions. Instead of looking at sales, inventory, supplier orders, and fulfillment separately, a connected system gives your team a clearer view of what is available, what is committed, what has been ordered, and what needs attention next.
This helps teams spot low inventory earlier, create supplier purchase orders with more confidence, adjust reorder points when needed, and avoid overselling across sales channels.
For growing eCommerce businesses, Ordoro’s inventory management software helps connect inventory, purchase orders, fulfillment, and multichannel workflows so teams can keep stock and orders moving together.
Frequently Asked Questions About Stockouts
What is a stockout?
A stockout happens when a product is unavailable because there is not enough inventory to meet demand. In eCommerce, this may mean a customer cannot buy the product, an order cannot be fulfilled, or shipping is delayed while the business waits for more inventory.
What causes stockouts in eCommerce?
Common causes of stockouts include inaccurate inventory counts, unexpected demand spikes, supplier delays, unclear reorder points, too little safety stock, disconnected sales channels, and poor visibility into purchase orders or inbound inventory.
How can eCommerce businesses prevent stockouts?
eCommerce businesses can prevent stockouts by keeping inventory counts accurate, forecasting demand, setting reorder points, keeping enough safety stock, tracking supplier purchase orders, and connecting inventory data across sales channels and fulfillment workflows.
How do reorder points help prevent stockouts?
Reorder points help teams reorder before inventory becomes critical. A reorder point tells the team when it is time to buy more based on sales velocity, supplier lead time, and safety stock.
How does safety stock reduce stockout risk?
Safety stock gives businesses extra inventory to cover unexpected changes, such as supplier delays, higher-than-expected demand, inventory count issues, or promotions that create more orders than planned.
Why do supplier lead times matter for stockout prevention?
Supplier lead times determine how long current inventory needs to last after a purchase order is placed. Longer lead times usually require earlier replenishment planning, higher reorder points, or more safety stock.
Can spreadsheets help prevent stockouts?
Spreadsheets can help with basic inventory tracking, but they become harder to manage as products, orders, suppliers, and sales channels grow. Stockout prevention depends on current data, and spreadsheets can become outdated quickly when updates are manual.
Keep Stockouts From Slowing Orders Down
Preventing stockouts is not about carrying endless inventory. It is about giving your team better visibility and clearer restocking signals before products run out. Forecasting helps you plan demand. Reorder points tell you when to act. Safety stock gives you a cushion. Supplier purchase orders help track what is on the way. Together, those pieces support a stronger inventory workflow.
Ready to manage inventory with more clarity? Start a free trial of Ordoro and see how connected inventory and purchasing workflows can support your next stage of growth.
