In-Stock Rate and IPI: How to Maintain High Availability

Amazon's in-stock rate metric in the IPI calculation focuses on your most popular products — specifically, products ranked in the top tier of your recent sales. It measures how often these products were available for purchase (in stock) versus out of stock over a recent period. For high-selling products, stockouts are the key risk. A 3-day stockout on a product selling 20 units per day does not just cost you 60 sales — it also depresses your IPI in-stock rate metric and can cause a temporary rank drop that takes weeks to recover from. Strategies to maintain high in-stock rates: calculate your replenishment lead time accurately (include FBA receiving time, which is currently 3-10 business days) and set your reorder point to trigger before you would realistically stock out accounting for that full lead time. Use FBA inventory age reports to monitor incoming shipments and flag if they are delayed. For high-volume holiday periods, send replenishment 4-6 weeks earlier than you think you need to — FBA receiving slows significantly in October and November. For products where stockouts are particularly costly (high-priced, high-velocity, few competitors), maintain a small safety stock to buffer against unexpected demand spikes or fulfillment center delays.