Amazon IPI Score Formula: How It Is Calculated

Amazon does not publicly disclose the exact mathematical formula for IPI calculation, but based on official documentation and seller community analysis, the score is derived from four primary factors with approximately the following relative weights: Excess Inventory Percentage (approximately 30-35% of score impact): the proportion of your FBA inventory units categorized as excess based on having more than 90 days of supply relative to recent sales velocity. Sell-Through Rate (approximately 30-35%): your last 90 days of sales divided by your average 90-day on-hand inventory. Stranded Inventory Percentage (approximately 15-20%): the proportion of your FBA units that have no active offer attached to them. In-Stock Rate for Popular Items (approximately 15-20%): how consistently your fastest-selling ASINs (those ranking high on recent sales) remain in stock. The algorithm appears to be a composite score where each factor is normalized to a sub-score and then weighted. This means a very low score in one factor can disproportionately pull down the overall IPI. Practical implication: a seller with excellent sell-through rate but high stranded inventory will score worse than expected from the sell-through data alone. All four factors need to be maintained simultaneously.