Stockout Revenue Loss Estimator
Every day a best-seller is out of stock, you're not just missing sales — you're losing customers to whoever has it in stock instead. This estimates the revenue and profit a stockout costs you, based on what you'd normally be selling.
What your result means
The calculator shows the revenue and gross profit you'd normally have made while a product was out of stock. Profit is the more useful number: it's what the stockout actually cost the business.
Treat it as a floor, not the full cost. It doesn't count ad spend still sending shoppers to an unavailable product, customers who switch to a competitor for good, or any drop in marketplace or search rankings.
How the stockout cost formula works
Lost revenue = Average daily units sold × Average selling price × Days out of stock Lost profit = Lost revenue × Gross margin
- Average daily units sold
- units per day before the stockout
- Average selling price
- what a unit typically sells for, after discounts
- Gross margin
- the share of each sale left after product costs
Use daily sales from a normal period before the stockout. Sales right before running out are often low because only a few sizes or colors were left.
Worked example
Worked exampleExample numbers
These match the calculator's default inputs.
| Input | Value |
|---|---|
| Average daily units sold | 15 |
| Average selling price | $35 |
| Gross margin | 45% |
| Days out of stock | 7 |
- Lost revenue = 15 × $35 × 7 = $3,675
- Lost profit = $3,675 × 45% = $1,653.75
How to prevent stockouts
- Reorder on time. A reorder point based on daily sales and lead time triggers orders before you run out.
- Hold enough safety stock on best-sellers. The safety stock calculator sizes the buffer for your worst restock cycles.
- Plan for peak season. Demand rises while suppliers slow down; the seasonal lead-time buffer calculator covers both, and the guide to lead time explains how to measure it.
- Pause ads on out-of-stock products so you don't pay for clicks you can't convert.
- Consider backorders when restock dates are short and reliable. The guide to backorders vs stockouts covers when they make sense.
Common mistakes
- Using sales from just before the stockout. In the days before running out, only a few sizes or colors are usually left, so sales are already depressed. Use a normal period.
- Counting only fully sold-out days. If key sizes or variants are gone, you're partly out of stock even with some units left. Count those days too, at a reduced rate.
- Ignoring wasted ad spend. If ads kept running to the product, add that spend to the cost.
- Forgetting substitutes. If many customers bought a similar product of yours instead, your real loss is smaller. If they went elsewhere, it may be bigger.
- Treating it as a one-off. Repeated stockouts on the same product point to a reorder point or safety stock that's set too low.
FAQ
Does this include customers who never come back?
No. It estimates the direct sales you'd normally have made while the product was out of stock. Lost repeat purchases, wasted ad spend and lower search rankings can add to the real cost, but they're hard to measure, so they aren't included.
What if customers buy a substitute instead?
Then your real loss is smaller, because some of the sale moves to another of your products. If you know roughly what share of customers switch, reduce the days or units to match.
Is a backorder a stockout?
Not quite. With a backorder, the customer still buys and waits for new stock, so the sale isn't lost unless they cancel. A stockout means the product can't be bought at all.