IPI (Inventory Performance Index)

Why IPI matters for an FBA seller

Amazon uses your IPI to decide whether you get unlimited FBA storage or a capped storage limit. Fall below Amazon's published threshold near the end of a quarter and you can be restricted in the next one, which means you physically cannot send in enough units to cover demand.

A low IPI is rarely one problem. It is usually a mix of slow movers eating your excess-inventory ratio, stranded listings you forgot about, and your best sellers dipping out of stock. Each of those is fixable, but only if you can see them before the score is locked in.

Product size is the hidden driver of your IPI

Amazon does not say this in the official documentation, but the strongest correlation we see in real seller accounts is product volume. IPI behaves like a measurement of how much throughput your account moves relative to the cubic feet of warehouse space it consumes. Two sellers can run identical sell-through, identical excess ratios, and identical in-stock rates, and the one selling larger items will end up with a noticeably lower score.

The mechanism is straightforward in practice. A pallet of small consumables turns the storage footprint over quickly, so the same dollar of revenue passes through far less Amazon warehouse space. A bulky item ties up cubic feet for the same number of unit sales, and the ratio Amazon is measuring slides against you. If your catalog skews toward oversize or heavy SKUs, expect a structurally lower IPI even when you are operating cleanly, and plan storage limits and restock cadence around that reality.

What you can actually control: prune large SKUs that do not earn their cubic feet, package efficiency on the items you keep, and lean harder on the small and standard-size winners. Removal orders on slow-moving oversize units pay back disproportionately because every cubic foot you reclaim helps the same ratio that is dragging the score.

How IPI connects to your restock decisions

IPI rewards the same behavior that protects revenue: keep fast movers in stock, and do not bury cash in inventory that will not sell for six months. Restock too little and your in-stock rate drops. Restock too much of the wrong SKU and your excess-inventory percentage climbs. Both pull the score down.

The practical move is to plan replenishment at the SKU level using real sell-through and lead time, not a flat reorder rule. Fix stranded inventory immediately, run down or remove aged units before they become excess, and prioritize inbound space for the SKUs that actually convert.