Stockout cost calculator
Sales that did not happen leave no line item, so the cost of a stockout is invisible until someone estimates it. This does the estimate: what the dark days sold in the weeks before, priced.
One SKU, one stockout. Daily rate from the weeks before it went dark, not the weeks it was out.
Days sellable inventory was zero while the page stayed up.
Price minus product, shipping, and payment costs.
Buyers who take another variant, or wait. The rest buy elsewhere.
Sales you never saw
135 units
£4,320 of revenue
Contribution lost for good
£1,944
After the demand that stayed with you.
A year of this, monthly
£23,328
If one SKU does this every month.
This number never appears in a report: sales that did not happen leave no line item. Any ad spend pointed at this product during those 9 days paid for traffic to an empty shelf on top of it.
How it works
Missed units = the daily rate before the stockout × days out of stock. Revenue at risk = missed units × price. Contribution at risk = revenue at risk × contribution margin. The substitution slider removes the share of demand that stayed with you — bought another variant, or waited — and what is left is contribution lost for good.
The estimate is deliberately simple and slightly conservative: it prices the units, not the second-order costs. Ad spend that ran against the empty page, the subscriber who churned after the miss, and the ranking the listing lost are all on top.
The yearly figure assumes one stockout like this per month, which for a store without a reorder discipline is not pessimistic. The point of the number is to buy the fix: the buffer the safety stock calculator sizes usually costs less than one of these.
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