The real cost of a stockout
When a product hits zero inventory, Amazon stops showing it as buyable — and it drops out of the search ranking signals that period would have generated. When it comes back, its recent sales history is weaker, which can reduce organic placement until the product regains traction. Add the direct impact on IPI (below) and it's clear why a stockout on a best seller costs far more than the revenue lost while it was out of stock.
IPI and the in-stock rate
The Inventory Performance Index (IPI) is the score Amazon uses to summarize the health of an account's FBA inventory. It's made up of four factors: excess inventory percentage, stranded inventory percentage (no active listing), sell-through rate, and the in-stock rate of your best-selling products. The score is recalculated weekly, on Mondays, based on the last three months of performance.
The minimum IPI threshold Amazon uses for storage limit decisions is 400 — down from 450 in previous years. Because the calculation looks back, a run of recent stockouts keeps weighing on the score for weeks, even after the inventory is back.
Restock Inventory: Amazon's own recommendation
Under Inventory > Inventory Planning > Restock Inventory, Seller Central shows each SKU's current inventory and Amazon's own recommended replenishment quantity, based on sales history and replenishment lead time — along with a suggested ship date so you don't run out before the next shipment reaches the fulfillment center.
Replenishment Alerts: the warning before you run out
Replenishment Alerts complement Restock Inventory by proactively warning you when a SKU is on track to go out of stock, before it actually happens — giving you room to create a shipment in time instead of finding out only after the product is already out of stock.
In practice: what to check every week
- Days of cover per SKU — how many days current inventory lasts at the recent sales pace.
- Real replenishment lead time — production/import time plus transit time to the fulfillment center, not a generic number.
- SKUs with a falling in-stock rate — an early sign of repeated stockouts, even before they actually hit zero.
- Seasonality and campaign spikes — a successful Ads campaign can speed up sell-through and bring the stockout earlier than the standard forecast.
How EcomVision helps
EcomVision's Inventory, Turnover, and Replenishment module combines real sales velocity, replenishment lead time, and Ads campaign spikes to flag stockout risk per SKU before inventory hits zero — not only when Amazon's own Restock Inventory is already at the limit.
