Stockout Cost Calculator
Estimate what a stockout costs. Enter units short, lost gross margin per unit, and any penalty costs to get the lost margin and total stockout cost, with the formula explained.
A stockout costs more than the sales you visibly miss. The immediate hit is the gross margin on every unit of demand you could not fill, and shortages often trigger direct extra costs on top: expedited freight, service-level fines, or paying more for a substitute. This tool adds those up into a first-order estimate of what one stockout event really cost.
How it works
Multiply the units of unfilled demand by the gross margin you lose on each, then add any direct penalty costs the shortage caused. The result is the immediate, measurable cost of the event; long-term customer damage comes on top of it.
The formula
Lost margin = units short x lost gross margin per unit. Stockout cost = lost margin + penalty costs. Use gross margin, not revenue: the cost of goods you did not ship is not a loss.
Worked example
Short 120 units at $18 gross margin each: lost margin = 120 x 18 = $2,160. Add a $500 expediting charge and the estimated stockout cost is $2,160 + $500 = $2,660.
Frequently asked questions
What should I include in penalty costs?
Direct costs triggered by the shortage: expedited or air freight to recover, contractual SLA fines, costs of sourcing a substitute, and extra handling for emergency orders. If a cost only happened because you stocked out, it belongs here.
What if customers backorder instead of walking away?
A backorder recovers the margin, so do not count those units as lost sales. Backorders still cost you, though: expediting, double handling, and goodwill. Count only truly lost demand in units short and put backorder-recovery costs in penalties.
Does this capture the full cost of stocking out?
No. Repeated stockouts push customers to competitors, and that long-term margin loss can dwarf the immediate hit. Treat this as a floor on the true cost, which is one reason it is usually worth buying insurance against stockouts with safety stock.
How do I prevent stockouts?
Safety stock is the main lever: size a buffer to a target service level with the safety stock calculator, then set your reorder point so replenishment starts before the buffer is needed.
Related tools
This is a planning estimate. Results depend on your inputs and assumptions; confirm against your own data before ordering.
- All unfilled demand is treated as lost sales at full gross margin.
- Penalty costs are known, direct, and attributable to this stockout event.
- One-off event view; it does not annualise or amortise costs.