A stockout occurs when an item is unavailable to meet demand at a particular location or channel.
How it works in retail
It can affect one product variant even when other sizes or colours remain available. Retailers track the duration and customer impact as well as the stock quantity.
A retail example
A store has several sizes of a shoe, but the size requested by a customer is unavailable and cannot be fulfilled from another location.
What to keep in mind
A sales report can hide unmet demand because an unavailable item cannot sell. Lost demand should not be treated as proven revenue without a suitable method.
Examples are illustrative. Terminology and measurement conventions can vary by business and market.