Divide the units you sold over a period by the average units you had available during that period, then express it as a percentage. If you sold 300 units and averaged 500 on hand, your sell-through rate is 300 / 500 = 60 percent. Amazon's FBA dashboard reports it as trailing 90-day units sold over your average available inventory.
Why does sell-through rate matter for Amazon sellers?
It is a direct measure of how hard your inventory dollars are working, and it feeds your Inventory Performance Index. A SKU with weak sell-through ties up cash, racks up storage fees, and drags the score that governs your storage limits, so a slow seller does double damage.
T. Brian Jones is co-founder and CTO of Inventory Hero. He leads the engineering behind its Amazon data pipeline, demand forecasting, and the AI platform that lets sellers talk to their live inventory, sales, and supplier data in plain language.
There is no single published target, since it depends on the product and the window you measure, but the practical benchmark is your IPI: sell-through is a heavily weighted input, and Amazon has historically applied a storage-limit threshold around an IPI of 400. Keep sell-through high enough that your IPI stays clear of that line, track the trend per SKU, and treat a falling rate as an early warning that a product is slowing before it becomes dead stock.
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Sell-through rate is the number of units you sold over a period divided by the average number of units you had available, expressed as a percentage or ratio. The short version: it is the most direct read on how fast a product moves, Amazon reports it as trailing 90-day sales over average inventory,1 and it feeds your IPI, so a slow seller both ties up cash and drags the score that governs your storage. Below is the formula, a worked example, and how to use it.
Sell-through rate = units sold in a period / average units available in that period
If you sold 300 units over a month and averaged 500 units on hand during it, your sell-through rate is 300 / 500 = 60 percent. Amazon's FBA dashboard reports its own version as trailing 90-day units sold divided by your average available inventory over that window. See the sell-through rate definition for the short form, and size it in the sell-through rate calculator.
To match Amazon's dashboard figure, run 90 days of sales against your average available over that same 90-day window. A single-month rate like the 60 percent above will not line up directly with the number Seller Central shows, so compare like windows to like windows. To pull the inputs yourself, take units sold from your Business Reports (Units Ordered by ASIN) and units on hand from the FBA inventory report; for Amazon's own figure, read it straight off the Inventory Performance dashboard.
Track it per SKU, not as a blended account number. The account average hides the slow movers that quietly cost you the most.
Two reasons it is one of the KPIs that most directly affects your money:
It is cash efficiency. A high sell-through means product moves before it racks up storage fees; a low one means cash sitting in a warehouse aging toward the aged-inventory surcharge.
It feeds your IPI. Amazon explicitly rewards healthy sell-through, so a SKU that turns slowly does double damage: it ties up capital and drags the score that governs your storage limits.
On the IPI point specifically: Amazon has historically applied a threshold (around 400) below which sellers face storage limits, and sell-through is one of the most heavily weighted inputs to the score. That makes a low or falling sell-through one of the fastest ways to push your IPI toward that line. Amazon has adjusted the exact threshold over time, so treat 400 as the historical reference point and check the current number in your own account. The practical takeaway does not change: protect sell-through and you protect your storage capacity.
That is why sell-through is worth watching closely, especially the trend. A falling sell-through is an early warning that a SKU is slowing before it becomes dead stock.
Sell-through is the signal for how much to reorder and how often:
Strong, steady sell-through can support deeper buys with confidence.
Weak sell-through should get smaller, more frequent orders so you are not committing cash to product that crawls.
Falling sell-through is a flag to slow or stop reordering and consider clearing the SKU before it ages. To operationalize it, pull the FBA Inventory Age report monthly; any ASIN whose sell-through has declined two periods running with an average age above 60 days is a reprice or clearance candidate.
Pair it with days of supply and lead time so the reorder quantity reflects both how fast it sells and how long it takes to arrive. For the full metric set, see the inventory KPIs that matter; for the restock system it feeds, restock planning.
The absolute sell-through number matters less than its direction, and it moves differently by product type. Seasonal SKUs spike and dip naturally, so a single-period dip is noise; steady staples should hold a stable rate, so a two-period slide is a real signal. That is why the 90-day window is more reliable than a 30-day snapshot: it smooths the noise and shows you the trend that actually predicts dead stock.
Sell-through rate is units sold over average units on hand, the cleanest single read on how efficiently a SKU converts inventory to sales, and the metric Amazon rewards through IPI. Track it per SKU, watch the trend more than the absolute number, and use it to decide how much to reorder and when to clear a slowing product.
Sell-through rate and its role in the Inventory Performance Index (IPI) are defined in Amazon Seller Central Help, "Inventory Performance Index" (sellercentral.amazon.com). Amazon has revised IPI components and thresholds over time; verify current details in your account. ↩