Inventory health is the full operational picture of how your Amazon stock is performing, not a single number. It covers how fast units sell, how many weeks of cover you are carrying, how much stock is aging toward long-term storage fees, and whether any of it is stranded or otherwise unsellable. IPI is Amazon’s own scorecard for one slice of this picture. Inventory health is the wider view we use to actually run the business, and it drives the decisions IPI alone cannot: what to reorder, what to liquidate, and where cash is trapped.
What Does “Inventory Health” Actually Mean?
Inventory health is a working diagnosis, built from several signals read together rather than any one metric read alone. A single number can look fine while the underlying picture is not. High sell-through on your bestseller can mask an understock that is about to cost you the Buy Box. A comfortable IPI score can sit on top of a pile of aged units quietly heading for long-term storage fees. We treat inventory health as a set of questions we ask of every SKU, not a dashboard tile:
- Sell-through rate: How fast a SKU is actually moving against the stock you are holding.
- Weeks (or days) of cover: How long current stock lasts at the current sales rate before you run out.
- Aged inventory: How much stock is sitting long enough to trigger long-term storage fees.
- Stranded inventory: Units physically at Amazon that are not listed for sale, so nothing about them can improve.
- Excess vs. understock: Whether a SKU is overbuilt for its sales rate, or thin enough to risk a stock-out.
- IPI: Amazon’s own score, built from four of the signals above, that gates your storage access.
IPI is useful because Amazon publishes it and ties consequences to it. But it is a compressed, backward-looking summary. It cannot tell you which SKU to reorder next week or which pallet of aged stock to liquidate before the surcharge hits. That is the gap inventory health fills. If you have not read it yet, our IPI score breakdown covers the 0-1,000 score, its four inputs, and how restock limits attach to it in detail. This post stays at the operating layer above it.
What Are the Core Signals of Inventory Health?
Sell-Through Rate
Sell-through rate is units sold over a period divided by average units on hand over that same period. It answers a simple question: is this SKU moving, or is it parking? A high sell-through rate with tight cover is a good problem, it means you are close to a stock-out on a winner. A low sell-through rate with heavy stock is the opposite problem, capital sitting still and racking up storage fees while it waits for demand that may not come.
Weeks of Cover
Weeks of cover is current available stock divided by average weekly sales velocity. It is the number we lean on most for reorder timing, because it converts a unit count into a runway. A SKU with 3 weeks of cover and a 6-week reorder lead time is already late. A SKU with 20 weeks of cover on a slow mover is tying up cash and courting long-term storage fees. Cover only means something next to lead time, so we always read the two together rather than either alone.
Aged Inventory and Long-Term Storage Fees
Aged inventory is stock that has sat in FBA past the point where it is still cheap to hold. Amazon’s long-term storage fee kicks in at 181 days for units that have not sold, and it is meaningfully more expensive than standard monthly storage. Watching age distribution across a SKU, not just current stock count, is what catches this before the surcharge posts. A SKU can carry a fine sell-through rate on its recent inbound units while an old batch from an earlier order quietly ages out underneath it.
Stranded Inventory
Stranded inventory is stock physically at a fulfillment center attached to a listing that is inactive, suppressed, or closed, so no customer can buy it. It still accrues storage fees while it sells nothing. This is usually the fastest fix on the list, because the cause is almost always a listing problem, not a demand problem. Amazon’s Stranded Inventory report in Seller Central names the ASIN and the specific reason.
Excess vs. Understock
Excess and understock are opposite failure modes on the same axis. Excess is stock built past what the sales rate justifies, the driver behind most IPI penalties and long-term storage exposure. Understock is stock thin enough to risk running out on a SKU that is actually selling, which costs you the Buy Box and often organic rank along with it. The healthy zone sits between the two, and it is different for every SKU depending on velocity, lead time, and how forgiving the product’s demand curve is.
How Do You Read Inventory Health in Seller Central?
No single Seller Central screen shows all of this together, which is a big part of why inventory health gets treated as one score instead of a picture. The pieces are scattered:
| Signal | Where to check |
|---|---|
| Sell-through rate | Inventory then Inventory Performance (also folded into IPI) |
| Weeks of cover / restock recommendations | Inventory then Manage FBA Inventory then Restock Inventory |
| Aged inventory / long-term storage risk | Inventory then FBA Inventory then Manage Excess Inventory / Inventory Age report |
| Stranded inventory | Inventory then FBA Inventory then Stranded Inventory |
| IPI score | Inventory then Inventory Performance |
Checking each report separately works, but it means the decision always lags the data by however long it takes to hop between five screens and reconcile them by hand. We covered the wider dashboard layout, and where the profit-relevant numbers actually live, in how to read your Seller Central dashboard.
How Do You Leverage Inventory Health? Turning Signals Into Decisions
Reading the signals is only half the job. The point of tracking inventory health is that it drives specific decisions, on a schedule, before a problem shows up as a rejected shipment or a surcharge on the statement.
- Reorder timing: Set reorder points from weeks of cover against real lead time, not a flat “reorder at X units” rule that ignores how fast a SKU is currently moving.
- Liquidating aged stock: Move units approaching the 181-day mark through a price drop, a lightning deal, or Amazon’s Outlet program before the long-term storage fee posts, rather than after.
- Protecting capital efficiency: Treat weeks of cover as a form of trapped cash. A SKU sitting at 25 weeks of cover is capital that is not funding the next order on something that actually sells.
- Avoiding stockouts on winners: Prioritize replenishment on your highest-velocity ASINs first, since a stock-out there costs both sales and the organic rank it can take weeks to rebuild.
- Fixing stranded units on sight: Clear listing issues immediately rather than batching them, since every day stranded is a day of storage fees on zero revenue.
None of these decisions are about the score. They are about margin and cash. A SKU can hold a perfectly acceptable IPI number while still bleeding money through aged units or a near stock-out on your best seller. That is why we always put inventory health decisions next to the P&L, not next to the score alone, the same discipline we walk through in why sales can rise while profit stays flat. If you are also weighing ad spend against a slower-moving SKU, the same cover math shows up in our ACoS vs. TACoS breakdown, since pushing ads at a slow mover to protect a score is not always the profitable move.
How Does Inventory Health Relate to IPI?
IPI is a compressed, four-input summary of inventory health, not a replacement for it. Sell-through rate and excess inventory percentage feed IPI directly. Stranded inventory percentage feeds IPI directly. But weeks of cover, aged-inventory risk ahead of the 181-day mark, and per-SKU capital efficiency do not appear in the score at all, they only show up in the reports behind it. A seller who manages purely to the IPI number can hold a healthy score while still carrying real cash sitting in slow stock or a live stock-out risk on a top seller. Manage the fuller picture and a good IPI score tends to follow as a byproduct, not the other way around.
This is the reason we built XBR to surface sell-through, cover, aged stock, and IPI side by side with SKU-level profit, instead of one score on its own screen. An inventory decision made without margin context is a guess dressed up as data. Our services and glossary both start from that same per-SKU view.