Amazon FBA Sell-Through Rate (STR) measures how fast your inventory moves through fulfilment centres. A low STR triggers higher storage fees, lower restock limits, and a falling IPI score, all of which compress profit before any other operational issue does. This guide covers the exact 2026 calculation, what counts as a healthy rate, the IPI cascade, and the specific actions that move STR fastest.
Key takeaways
- STR = units shipped over 90 days / average inventory over the same period, calculated and reported by Amazon for FBA sellers.
- Amazon classifies STR as Excellent (above 7), Good (3-7), Fair (1-2), Poor (below 1). Below 1 means you held more stock than you sold.
- STR is one of four IPI components alongside excess inventory %, stranded inventory %, and in-stock rate.
- An IPI below 400 can trigger restock-limit reductions; below 300 historically risked storage suspension during peak.
- The fastest STR fixes are removal orders for stranded inventory, lightning deals on slow-movers, and tighter shipment sizing.
What is the Amazon FBA Sell-Through Rate?
FBA Sell-Through Rate is Amazon's measure of how efficiently your inventory moves through their fulfilment network. It compares units sold to average units held over a rolling 90-day window. The metric is reported on the Inventory Performance Dashboard inside Seller Central and updates automatically.
STR is one of several performance metrics Amazon tracks per seller account. It directly affects what you pay in monthly storage fees, your maximum FBA inventory, and your IPI score, which in turn affects your restock limits.
How Amazon calculates FBA Sell-Through Rate
STR = total units shipped (last 90 days) / average inventory level (last 90 days)
If you shipped 150 units from an average FBA inventory of 120, your STR is 1.25. Anything above 1 means you sold more than your average held inventory; below 1 means you sat on stock.
Note: this is FBA-specific. Most non-Amazon retail discussions of "sell-through rate" use a different formula, expressed as a percentage:
General STR (%) = (units sold in period / inventory at start of period) × 100
If you started May with 500 units and sold 380, your retail-style STR is 76%. Don't mix the two formulas. When you're optimising for Amazon, use Amazon's version.
How to find your STR in Seller Central
Inventory tab → Inventory Performance Dashboard. STR appears both as an account-level number and per-product. Per-product STR is what you should focus on for SKU-level decisions; account-level STR is what Amazon uses to calibrate your IPI.
What counts as a healthy STR
Amazon's published bands:
| Band | STR range | What it means |
|---|---|---|
| Excellent | Above 7 | You're moving 7+ units for every unit held on average. Aggressive turnover; risk of stockouts. |
| Good | 3-7 | Healthy turnover with comfortable buffer. Most profitable sellers sit here. |
| Fair | 1-2 | Inventory is moving but slowly. Storage fees start eating margin. |
| Poor | Below 1 | You held more than you sold. Restock limits will tighten and IPI will drop. |
Sustaining an STR above 7 is harder than it looks. If your average inventory is 100 units and you sell 700 in the period, you're carrying less than two weeks of stock at any given time. A single supplier delay or demand spike can stock you out, and Amazon penalises stockouts on the in-stock-rate component of IPI. Aim for the Good band (3-7) unless your category has unusually fast lead times.
The IPI cascade: why STR matters more than it looks
STR is one of four inputs to the Amazon Inventory Performance Index (IPI), Amazon's headline number for inventory health.
| IPI input | What it measures | Why it matters |
|---|---|---|
| Excess inventory % | Units forecast to sit longer than 90 days at current sales rate | Drives long-term storage surcharges |
| Sell-Through Rate | Units shipped / avg inventory in 90 days | Restock-limit calibration |
| Stranded inventory % | Units in FCs that can't be sold (closed listings, errors) | Pure waste, no revenue possible |
| In-stock rate | Days in stock / total days for active SKUs | Lost-sales protection |
An IPI below 400 historically reduced restock limits. Below 300 risked storage suspension during Q4 peak. Amazon adjusts these thresholds periodically; the current targets are visible in the Inventory Performance Dashboard. Improving STR alone won't lift IPI if stranded or excess inventory percentages are bad, so address all four components together. The full guide to IPI scores walks through the calculation in detail.
How to improve a low STR (in priority order)
- Resolve stranded inventory first. Stranded units inflate your average inventory but generate zero sales, so they tank STR for free. Inventory tab → Fix Stranded Inventory. This is usually the fastest single move.
- Issue removal orders on aged stock. Anything older than 270 days at low velocity should leave the FC. Removal fees are typically less than the storage cost you'll incur over another 90 days.
- Run lightning deals or coupons on slow-movers. Even at break-even, clearing slow inventory restores STR and improves your best seller rank, which compounds future sales.
- Right-size your replenishment. Send smaller, more frequent shipments instead of one large quarterly order. This drops average inventory without dropping unit sales.
- Increase Sponsored Products spend on top-velocity SKUs. ACoS-tolerable PPC on the top 20% of your catalogue accelerates turnover where it has the highest margin yield.
- Optimise listings on slow-movers. Update titles, bullets, A+ content, and main images. See Amazon A+ Content for the format that converts best.
- Bundle slow-movers with fast-movers. Pair a slow SKU with a complementary fast SKU at a small discount; this clears the slow without cannibalising margin.
STR and your insurance exposure
This connection isn't obvious until you've had a claim. Amazon's $10K monthly sales threshold for mandatory Amazon seller insurance is calculated on gross sales, not on units. Sellers with high STR + high prices hit the threshold faster than sellers with low STR + low prices. The earlier you cross $10K/month, the earlier the 30-day insurance compliance clock starts ticking. See the Amazon Certificate of Insurance guide for the upload process.
If you sell imported goods from China or any product category with elevated recall exposure, low STR also extends your liability tail. The longer aged stock sits in FCs, the more units enter the market with weakening QC oversight from the original supplier.
Frequently asked questions
What is a good Amazon FBA Sell-Through Rate?
Amazon classifies STR as Excellent (above 7), Good (3-7), Fair (1-2), and Poor (below 1). Most profitable FBA sellers sit in the Good band. Sustaining above 7 is risky for stockouts; below 1 triggers restock-limit penalties.
How is FBA Sell-Through Rate calculated?
Total units shipped over the last 90 days divided by average inventory level over the same 90 days. Amazon calculates this automatically on the Inventory Performance Dashboard. The formula is different from retail-style STR, which is expressed as a percentage of starting inventory.
How does STR affect Amazon storage fees?
Low STR means slow inventory movement, which extends time in fulfilment centres and triggers Amazon's long-term storage surcharges (typically applied at 271 and 365 days). High STR keeps inventory cycling through faster than the surcharge thresholds. STR also feeds into IPI, which directly determines your maximum FBA storage volume.
Can I improve my STR quickly?
Yes. Resolving stranded inventory and issuing removal orders on aged stock can lift STR within a single 90-day window. Lightning deals and coupons on slow-movers are the next-fastest levers. Pricing and listing changes take longer to show up in the metric.
What is the relationship between STR and IPI?
STR is one of four inputs to your Amazon IPI score. The others are excess inventory percentage, stranded inventory percentage, and in-stock rate. All four contribute, so STR alone won't fix a poor IPI if the other three are unhealthy.
Bottom line
FBA Sell-Through Rate is a leading indicator of inventory health and a direct input to storage fees, restock limits, and your IPI score. Aim for the Good band (3-7) unless your category supports faster turnover without stockout risk. The fastest fixes are clearing stranded units, running removal orders on aged stock, and discounting slow-movers; the slowest fixes are pricing and listing-quality changes.
If your STR is dragging because you over-ordered ahead of a sales push, that is recoverable. If it is dragging because the underlying SKU does not move, no inventory tactic will save it; the answer is to drop the SKU. For broader Amazon-seller operational coverage, see the Amazon seller insurance guide and the eCommerce insurance buyer's guide.
Related reading: Amazon IPI scores, Amazon Best Seller Rank, Amazon inventory management.