Every Amazon seller who uses FBA has experienced that sinking feeling: you check your account health dashboard and discover your IPI score dropped below the threshold. Suddenly, your storage limits are slashed, and you can’t send in enough inventory to cover next month’s sales. The Inventory Performance Index is Amazon’s way of grading how well you manage the stock sitting in their fulfillment centers, and it directly controls how much space they’ll let you use.
How the IPI Score Works
Amazon calculates your IPI on a scale of 0 to 1,000, updated weekly. The minimum threshold has fluctuated over the years. It sat at 500 for a long time, dropped to 450 in some periods, and can change with little warning. When your score falls below that line, Amazon imposes storage volume limits on your account, capping how many cubic feet of product you can have in their warehouses. Sellers above the threshold get essentially unlimited storage (within reason).
Four factors feed into the calculation. Excess inventory percentage measures how much of your stock Amazon considers overstocked, meaning it’s projected to sit for more than 90 days based on current sell-through rates. FBA sell-through rate tracks how many units you move relative to what you store over the trailing 90 days. Stranded inventory percentage captures listings where stock is in a fulfillment center but the listing is inactive, so it can’t sell. FBA in-stock rate measures whether your popular items stay available or run out frequently.
Amazon doesn’t publish the exact weighting of each factor. Sellers have reverse-engineered rough estimates through experimentation. Excess inventory and sell-through rate seem to carry the most weight, while stranded inventory can tank your score fast if left unaddressed even for a few days.
Why a Low Score Costs Real Money
Storage limits are the obvious penalty. But the ripple effects go deeper. If you can’t send in enough inventory, you stock out on your best sellers. Stockouts kill your organic ranking on Amazon, and recovering that ranking after a restock can take weeks. During Q4, when storage limits matter most, a low IPI can mean leaving tens of thousands of dollars on the table because you simply can’t get product into FBA.
Amazon also charges aged inventory surcharges (formerly long-term storage fees) on units sitting longer than 181 days, with steeper penalties at 271 days and beyond. A low IPI usually correlates with high aged inventory, so you’re paying extra to store products that aren’t moving while simultaneously being told you can’t store more of the products that do move. It’s a frustrating cycle.
Practical Ways to Keep Your IPI High
The math is straightforward: send in what sells and don’t let dead stock accumulate. In practice, that’s hard to execute. Demand forecasting errors, supplier delays, seasonal shifts, and listing suppression all conspire against clean inventory management.
Removing excess inventory before it triggers the 90-day threshold is one direct lever. You can create removal orders to have Amazon ship stock back to you or destroy it. Neither option feels great, but the cost of a removal order (roughly $0.50 to $1.00 per unit depending on size) is often less than the combined hit of storage fees and a cratered IPI.
Fixing stranded inventory requires monitoring your account daily. Listings go inactive for dozens of reasons: a brand registry complaint, a category change, a missing item condition note, or a pricing error. Every day a listing sits inactive with inventory behind it, your score takes a hit.
Where a 3PL Fits Into IPI Management
Working with a prep service changes the equation. Instead of shipping everything directly to FBA and hoping your forecasts were right, you hold buffer stock at a 3PL warehouse and replenish Amazon in controlled batches. This keeps your FBA inventory lean, your sell-through rate high, and your excess inventory percentage low.
A prep center like MeisterPrep can turn around replenishment shipments quickly, often within 24 to 48 hours of receiving your request. That speed means you can run tighter inventory at Amazon without the stockout risk. You keep more product at the 3PL where storage is cheaper per cubic foot than Amazon’s fees, and only push units into FBA as sales data justifies it. For sellers managing hundreds of ASINs, this buffer stock strategy is often the difference between an IPI above 600 and one hovering dangerously near the cutoff.
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