Stockout Cost Calculator
Estimate the total cost of running out of stock, including lost profit, lost revenue, and the impact of customer churn. Use this to justify investment in safety stock and inventory buffers.
Enter your average daily sales, profit margin, stockout duration, and customer penalty to estimate the total cost of running out of stock, including lost profit and potential customer churn.
Average units sold per day
Contribution margin per unit
Duration of stockout
Cost per customer lost permanently
Percentage of affected customers that leave permanently
Formula
Stockout Cost = (Daily Sales × Days OOS × Profit/Unit) + (Daily Sales × Days OOS × % Lost Forever × Customer Penalty)
Stockout cost includes two components: direct lost profit from forgone sales, and indirect cost from customer churn. The first term calculates lost contribution margin. The second term models the lifetime value loss from customers who switch to competitors.
Worked Example
100 units/day, $15 profit each, 5-day stockout, $50 customer lifetime value penalty, 10% churn.
Units affected = 100 × 5 = 500 units
Lost revenue = 500 × $15 = $7,500
Customers lost = 500 × 10% = 50 customers
Churn cost = 50 × $50 = $2,500
Total cost = $7,500 + $2,500 = $10,000
A 5-day stockout costs $10,000 when factoring in both lost sales and permanent customer churn. This justifies investment in better demand forecasting and safety stock buffers.
Frequently Asked Questions
Use this in your workflow
Use this calculator with the Safety Stock Calculator to optimize inventory levels. Pair with the Inventory Turnover Calculator to assess overall inventory health. Browse all Free Business Calculators.
When to use this calculator
- →Evaluating the financial impact of past stockouts to improve future planning
- →Justifying investment in higher safety stock levels or better demand forecasting
- →Assessing the trade-off between carrying cost and stockout risk
- →Prioritizing which SKUs to focus on for improved inventory control
Worked example: impact of stockout on retail
A useful reference before entering your own figures above.
| Metric | Value |
|---|---|
| Average daily sales | 50 units |
| Profit per unit | $25 |
| Stockout duration | 7 days |
| Units affected | 350 units |
| Lost profit (direct) | $8,750 |
| Customers affected | 350 customers |
| Churn rate | 5% |
| Customer lifetime value penalty | $100 |
| Churn cost (indirect) | $1,750 |
| Total stockout cost | $10,500 |
A 7-day stockout on a popular item costs over $10,000 in lost profit and customer defection. This justifies investment in better demand forecasting or higher safety stock to prevent such events.
Common mistakes
- !Using revenue instead of profit. Use your contribution margin per unit for accuracy.
- !Underestimating customer churn. Research your historical data to get realistic percentages.
- !Ignoring lost customer lifetime value. Some customers never return after a stockout.
- !Forgetting to factor lead time. If your lead time is 14 days, your exposure is 14 days, not 1.
Responsible inventory planning
Stockout cost is one side of the inventory trade-off. Higher safety stock reduces stockout risk but increases carrying cost (storage, capital, obsolescence). Use this calculator to quantify the downside of stockouts, then use the Holding Cost Calculator to compare against the cost of extra inventory. The optimal inventory level balances both costs.
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Frequently asked questions
What is a stockout cost?
Stockout cost is the total financial impact of running out of inventory, including lost profit from forgone sales and the cost of customer churn. It does not include carrying cost or ordering cost.
How do I estimate customer churn from stockouts?
Customer churn depends on product type and availability of alternatives. For commodity items, churn may be 5–10%. For specialty items, 1–3%. For critical components, churn can approach 100%.
Should I use revenue or profit in the calculation?
Use profit (contribution margin), not revenue. If you sell $100 in goods with $15 profit margin, the lost profit is $15, not $100. This gives a realistic cost estimate.
How does this link to safety stock?
Safety stock is the buffer inventory held to avoid stockouts. Higher safety stock reduces the frequency and duration of stockouts, lowering total stockout cost. Use this calculator to justify the investment.
Should I include ordering lead time?
Yes. If a stockout occurs due to lead time, use the replenishment lead time as the stockout duration. Alternatively, use the Reorder Point calculator to optimize order timing.
What if I have multiple SKUs?
Calculate stockout cost for each SKU separately, then sum the results. High-velocity, high-margin items typically justify higher safety stock investment.