Stockout
Definition
A stockout occurs when inventory of an item is exhausted and demand cannot be met from available stock. It results in lost sales, backorders, expediting costs, and eroded customer trust.
In Practice
Stockouts have several root causes: forecast error, supplier delays, inaccurate inventory records showing stock that is not physically there, quality holds, and allocation mistakes that put stock in the wrong location. Diagnosing which cause dominates matters, because each has a different fix; adding safety stock does nothing for a record-accuracy problem.
The true cost extends beyond the missed sale. In retail, studies consistently show a substantial share of shoppers facing an empty shelf either buy a competitor's product or leave the store entirely, and repeated stockouts permanently shift buying habits. In manufacturing, a stocked-out component can idle an entire line, multiplying the cost of one cheap part into thousands of dollars per hour.
Planners manage stockout risk through service level targets, safety stock sized to demand and lead-time variability, and reorder points that trigger replenishment early enough. Tracking near-misses, times inventory dipped below safety stock, gives early warning before customers ever see a gap.
Related Calculators
Related Terms
The target probability of not stocking out during a replenishment cycle, or more broadly the standard of product availability promised to customers. It is the key input for sizing safety stock.
BackorderA customer order, or portion of one, accepted for fulfillment despite the item being out of stock, to be shipped when inventory becomes available. Managing backorders means tracking, prioritizing, and clearing this unmet demand.
Lead TimeLead time is the elapsed time between initiating a process, such as placing an order, and its completion, such as receiving the goods. It is one of the most important inputs to inventory, planning, and customer promise decisions.
Demand ForecastingDemand forecasting is the practice of estimating future customer demand using historical data, statistical models, and market knowledge. It provides the quantitative foundation for demand planning, inventory targets, and capacity decisions.