Definition
A stockout occurs when customer demand exists for a product but inventory has been depleted to zero and cannot be fulfilled immediately. Unlike a backorder — where demand is captured and will be fulfilled when stock arrives — a stockout typically results in lost sales when customers go to a competitor rather than wait. Stockouts are measured as stockout rate (the percentage of order lines that cannot be fulfilled from stock) or stockout events (the frequency with which any SKU hits zero inventory within a period). IHL Group estimates global retail stockout losses at $1.77 trillion annually. For distributors, stockouts on A-items are particularly damaging because they affect the highest-revenue products and the customers most likely to have alternatives.
Why It Matters
A single stockout on a customer's critical part can cost more in relationship damage than the product is worth in annual revenue. Studies consistently show 30–50% of customers who experience a stockout try a competitor's product — and 25–35% of those never return. Stockout prevention on high-value SKUs is both an inventory optimization problem and a customer retention strategy. Safety Stock Calculator →
Frequently Asked Questions
What causes a stockout?
Stockouts are caused by: inaccurate demand forecasts (actual demand exceeds forecast), insufficient safety stock (buffer is too thin for the variability encountered), supplier delivery failures (shipment late or incomplete), poor reorder point settings (order triggered too late), and demand spikes from promotions or seasonal events that were not anticipated.
How do you measure stockout rate?
Stockout rate = (number of order lines that could not be fulfilled from stock / total order lines received) × 100. A rate above 2–3% signals a systemic inventory planning problem. Track stockouts by SKU category to identify whether the problem is A-items (typically a safety stock problem) or C-items (typically a demand forecasting problem).
What is the hidden cost of a stockout?
The direct cost of a stockout is the lost margin on the sale. The indirect costs are larger: emergency expedite freight (often 3–10× standard shipping), customer service labor for calls and apologies, and customer attrition (30–50% of stockout customers try a competitor). For A-item stockouts with major accounts, the total cost can exceed $10,000 per event.