Stockout Rate
Stockout rate is the percentage of active SKUs, or SKU-days, with zero available inventory during a period, sometimes measured instead as the share of orders affected.
Why it matters for ecommerce brands
Stockout rate shows how much of your catalog was unavailable to buy, which means lost sales that never appear in order data. On marketplaces, stockouts can also cost search rank that takes time to rebuild. Weight it by sales to see whether stockouts hit best sellers or the long tail. For example, 200 SKUs over 30 days give 6,000 SKU-days. If 270 of those were at zero, the stockout rate is 4.5%. If most of those days belong to top sellers, the revenue impact is far larger.
Formula and calculator
Stockout rate = SKU-days out of stock ÷ total active SKU-days × 100
Common questions
- How do you calculate stockout rate?
- A common method counts SKU-days: the number of days each active SKU had zero available stock, divided by total active SKU-days in the period. In-stock rate is 100% minus the stockout rate.
- What is the difference between stockout rate and in-stock rate?
- They are two sides of the same number. In-stock rate is 100% minus the stockout rate, so a 4.5% stockout rate means a 95.5% in-stock rate.
- How do you estimate sales lost to stockouts?
- Multiply each SKU's days out of stock by its average daily sales when in stock. This is an estimate, since some customers wait or buy a substitute.