Amazon’s Inventory Performance Index (IPI) is a score from 0 to 1,000 that measures how efficiently FBA sellers manage inventory inside Amazon’s fulfillment centers. We pay attention to it because it gates your storage. Stay above Amazon’s current minimum threshold and you keep unlimited storage across your FBA product types. Fall below it and Amazon caps how much stock you can send in. The threshold sits at 400 today, but Amazon has moved it before, so we treat any fixed number as subject to change.
What Does Amazon IPI Measure?
IPI measures how efficiently you use Amazon’s fulfillment capacity. Warehouse space is finite, so Amazon favors inventory that sells quickly over stock that sits for months. The way we read it, the score penalizes three behaviors: holding more stock than your sales rate justifies, letting unlisted units sit idle, and stocking out of your best sellers. Amazon does not publish the exact formula, but it names four factors that drive the score:
- Excess Inventory Percentage: The share of your FBA units Amazon considers overstocked. Amazon calculates excess from weeks of supply on hand against your current sales rate. Units carrying more supply weeks than the threshold get flagged as excess and pull the score down.
- Sell-Through Rate: How quickly your inventory sells against the average inventory on hand. Amazon takes units sold and shipped over the last 90 days and divides by the average units at fulfillment centers over that window. Higher is better.
- Stranded Inventory Percentage: The share of your FBA inventory that is not buyable because the listing is inactive, suppressed, or closed. Stranded units take up warehouse space and sell nothing.
- In-Stock Rate: Whether your top-selling ASINs are in stock. Running out on a high-velocity item reads as weak replenishment planning and drags this piece of the score.
Amazon weights these factors, and in our experience excess inventory and sell-through carry the most influence. The score updates weekly. Because the math runs on a 90-day rolling window, the fixes you make this week take time to register fully in the number.
Where Do You Find Your IPI Score in Seller Central?
Your IPI score lives in Seller Central under Inventory then Inventory Performance, or Inventory then FBA Inventory depending on your account view. The dashboard shows the current score at the top, a breakdown of each factor, and the ASINs hurting the score most. You can also open it directly at sellercentral.amazon.com/inventory-performance/dashboard with a login.
The dashboard also lists “Estimated Potential Score Increase” suggestions. These are specific moves, like removing excess units or relisting stranded inventory, that Amazon estimates would raise the score by a stated amount. We use them as a starting map, not gospel, because the estimates assume nothing else changes.
What Happens If Your IPI Score Falls Below the Threshold?
Fall below Amazon’s minimum threshold and you face storage capacity restrictions across all FBA product types plus ASIN-level restock limits on individual SKUs. Shipments that exceed your allowed capacity get rejected at the fulfillment center. The threshold is 400 right now, and sellers who hold above 400 for two consecutive weekly check periods qualify for unlimited storage per product type.
Amazon adjusts the threshold from time to time and communicates changes through Seller Central announcements and email. It sat at 450 before Amazon lowered it to 400. We always confirm the current number inside the account rather than trusting a figure from an old article, because program terms move.
A low IPI also exposes you to storage utilization surcharges on top of standard monthly storage fees. Aged inventory surcharges trigger faster than they used to as well. Long-term storage fees now start at 181 days rather than the old 365-day mark. A rejected shipment during peak season, exactly when you need inventory on hand, costs you sales rank and Buy Box share directly. That is the case we see most often, and it is the one we work to prevent.
How Do You Improve Your Amazon IPI Score?
1. Reduce Excess Inventory
Excess inventory is usually the biggest drag on a low score. Because it weighs more heavily than the other factors, we address it first for the fastest lift. The moves we reach for:
- Create a removal or disposal order to pull excess units out of FBA. Removal ships units back to you, disposal has Amazon destroy them. Disposal is cheaper per unit and makes sense for low-value or unsellable stock.
- Run a price promotion or lightning deal to speed up sell-through on slow movers. Moving inventory faster clears excess flags sooner than waiting on organic sales.
- Use Amazon’s Outlet program for overstock. These are discounted listings on the Amazon Outlet page, which Amazon actively merchandises to bargain shoppers.
- Recalibrate reorder quantities going forward. If an ASIN keeps building excess, the send-in quantity or reorder point needs to match the actual sell rate.
2. Fix Stranded Inventory
Stranded inventory is often the fastest fix, because the root cause is usually an inactive or suppressed listing you can resolve in minutes. Amazon gives you a Stranded Inventory page in Seller Central that names each affected ASIN and the exact fix. The common causes we run into:
- A listing was closed or deleted while FBA stock remained
- A listing was suppressed for a missing required attribute, like a main image, title, or category-required field
- A listing was merged or split and the old ASIN went inactive
Fix the underlying listing and the stranded units clear within 24 to 48 hours as Amazon recalculates availability.
3. Improve Sell-Through on Key ASINs
Sell-through improves when sales go up or average inventory on hand comes down. The tactics we use:
- Increase advertising spend on slow movers that still hold acceptable margins. We watch the true cost here against total advertising cost of sales, which is the point of our ACoS vs TACoS breakdown.
- Improve listing quality, meaning images, title, and bullets, to raise conversion on the organic traffic you already get
- Reduce the quantity you send in for the next replenishment until sell-through normalizes
4. Hold In-Stock Status on Top Sellers
Stock-outs on high-velocity ASINs hurt the in-stock component of IPI and also damage organic rank. A listing can drop a long way in search during a stock-out and may not recover the moment you restock. Accurate reorder points built from lead time and sales velocity are the foundation here, and they are the piece most sellers underestimate.
What Is the Difference Between IPI, Restock Limits, and Storage Volume?
Amazon uses three related constraints to manage FBA inventory access. IPI is the performance score. Restock limits and storage volume are the capacity mechanisms it influences. You can have plenty of storage volume and still hit a restock limit on a single fast mover, so we plan shipments against all three rather than watching the score alone.
| Constraint | What it controls | Where to check in Seller Central | How IPI affects it |
|---|---|---|---|
| IPI Score | Your overall inventory efficiency rating (0 to 1,000) | Inventory then Inventory Performance | Is the score itself |
| Storage Volume | Total cubic feet available across all product types | Inventory then FBA Inventory then Manage Excess Inventory | Sellers below the threshold face volume caps. Above the threshold for two consecutive weeks qualifies for unlimited volume |
| Restock Limits | Unit cap per ASIN or product type category | Inventory then Restock Limits | A low IPI tightens restock limits at the ASIN level, independent of overall storage volume |
Check both the IPI dashboard and the Restock Limits section in Seller Central to see your complete inventory access picture. One without the other leaves you guessing.
If you run a large SKU catalog, especially with seasonal patterns, IPI is easier to manage when you can see the trend over time next to per-SKU sell-through. This is where our services come in. We surface IPI alongside SKU-level P&L so an inventory decision carries margin context, not just storage efficiency. That is the difference between clearing units to protect a score and clearing the right units.