Stockout
Also known as: out of stock, out-of-stock
When inventory hits zero and demand cannot be fulfilled — causing lost sales, customer frustration, and often a permanent switch to a competitor.
A stockout happens when demand for a product exists but you have zero units left to fulfil it. It is the event that inventory management exists to prevent: a customer wants to buy, and you cannot sell.
The immediate cost is the missed sale. The deeper cost is often larger: research consistently shows that roughly a quarter to a third of shoppers who hit an out-of-stock item will buy from a competitor rather than wait for restock. For products customers buy regularly, that can mean a permanently lost customer, not just a single lost order.
Stockouts are usually caused by one of four things: demand that exceeded the forecast, a supplier who delivered late, a reorder point that was set too low, or simply no system in place to watch stock levels and flag a warning in time. The last cause is the most common and the most avoidable.
Stockouts also cascade. A missing component can stall production. A missing bestseller can push a customer's entire basket to a competitor. In multi-location businesses, a stockout at one site cannot always be rescued by a transfer if other sites are also running thin.
The defences against stockouts work in layers: safety stock acts as a buffer against demand spikes and late deliveries, accurate reorder points trigger restocking early enough for replenishment to arrive in time, and inventory software monitors stock levels automatically so the trigger is never missed.
Put it into practice
Frequently asked questions
- What causes a stockout?
- Stockouts are usually caused by one of four things: demand that exceeded the forecast, a supplier who delivered late, a reorder point that was set too low, or no system in place to monitor stock levels and trigger restocking in time. The last cause is the most common and the most preventable.
- How much does a stockout cost?
- Beyond the immediate lost sale, research consistently shows that roughly a quarter to a third of shoppers who hit an out-of-stock item will buy from a competitor rather than wait. For products customers buy regularly, that can mean a permanently lost customer. In B2B contexts a stockout can stall production or break a supply commitment.
- What is the difference between a stockout and a backorder?
- A stockout means you have zero inventory and cannot immediately fulfil the order. A backorder means the customer has placed the order and you will fulfil it once stock is replenished. A backorder keeps the sale; a stockout risks losing it to a competitor entirely.
- How do you prevent stockouts?
- The core defences are: hold appropriate safety stock to absorb demand spikes and late deliveries, set accurate reorder points so replenishment orders are triggered early enough, and use inventory software to monitor levels automatically so the trigger is never missed.
Related terms
- Safety StockExtra inventory held as a buffer against demand spikes and supplier delays so you do not run out.
- Reorder PointThe inventory level that triggers a new purchase order, calculated so replenishment arrives before you sell out.
- BackorderAn order for a product that is temporarily out of stock, to be fulfilled once it is replenished.
Run it in one system
VNDLY tracks stock, orders, and suppliers together so terms like this stop being theory and start being automatic.