Your IPI score controls how much you can store in FBA. Learn the 4 factors, current thresholds, and 7 strategies to improve your score fast.
Mar 11, 2026 · 14 min · 3,800 words
Your Amazon IPI score is a number between 0 and 1,000 that determines how much inventory you're allowed to store in FBA warehouses. Drop below 400, and Amazon caps your storage capacity. Drop further, and you can't send in new shipments at all. For sellers doing $50K+/month, a low IPI score isn't just a dashboard metric. It's a revenue limiter.
This guide explains exactly how Amazon calculates your IPI score in 2026, what each factor weighs, the current thresholds, and the specific actions that move your score fastest. We've also included the connection between IPI and storage fees, because your score directly affects what you pay to store inventory.
IPI is calculated from four factors: excess inventory %, sell-through rate, stranded inventory %, and in-stock rate. The first two carry the most weight. Maintaining 45-day DOI across your catalog and resolving stranded listings within 48 hours is the fastest path to a 500+ IPI score.
The Inventory Performance Index (IPI) is Amazon's composite metric for evaluating how efficiently you manage FBA inventory. Amazon introduced IPI in 2018 to encourage sellers to maintain healthy inventory levels: not too much (driving up storage costs), not too little (creating stockouts).
According to Amazon's IPI documentation, the score updates weekly and is visible in Seller Central under Inventory > Inventory Planning > Performance. Amazon checks your IPI at two evaluation periods: the last 6 weeks of each quarter, with limits applied the following quarter if you're below threshold.
0-399
Storage limits enforced next quarter
400-549
No limits, room to improve
550+
Optimal inventory management
Amazon's IPI threshold has changed multiple times since launch. It started at 350, moved to 500 in 2020 during COVID, then settled back to 400 in 2021. Amazon reserves the right to change the threshold based on fulfillment center capacity, so maintaining a buffer above 400 (ideally 500+) protects against future changes.
Amazon doesn't publish the exact IPI formula, but they do reveal the four components. Based on seller testing and Amazon's IPI documentation, here's how they're weighted:
This measures what percentage of your FBA units Amazon considers "excess." Amazon defines excess as units where the cost of holding them exceeds the cost of reducing the price or removing them. If you're holding 90+ days of supply for slow movers, this metric suffers.
Target: Under 5% of your FBA units flagged as excess
Calculated as units sold and shipped over the last 90 days divided by average FBA inventory during the same period. Higher sell-through = better IPI. This is the flip side of excess inventory. If you're selling through stock efficiently, both metrics improve.
Target: Sell-through rate above 5 (units sold ÷ average units in stock)
Stranded inventory sits in FBA but isn't listed for sale. Common causes: listing suppression, pricing errors, expired products, or catalog issues. Stranded units cost you storage fees without any possibility of generating revenue.
Target: 0% stranded (resolve within 48 hours)
Measures what percentage of your replenishable FBA ASINs have been in stock over the last 30 days. Frequent stockouts on popular items hurt this metric. It's weighted lower than excess inventory but still matters, especially for brands with high-velocity products.
Target: Above 90% in-stock rate for replenishable ASINs
Here's the tension: Amazon wants you to have low excess inventory (send less) AND high in-stock rate (never run out). You can't optimize both by guessing. You need precise DOI tracking to maintain the sweet spot: enough stock to avoid stockouts, not so much that you're flagged as excess.
If your IPI drops below 400 during an evaluation period, Amazon enforces storage volume limits for the following quarter. These limits cap the total cubic feet of inventory you can store in FBA, calculated separately for standard-size and oversized items.
| Impact | IPI 400+ | IPI Below 400 |
|---|---|---|
| Storage Capacity | Unlimited | Capped (volume limit) |
| Shipment Creation | No restrictions | Blocked when at capacity |
| Overage Fees | None | $10/cu ft/month for excess |
| Product Launches | Send inventory freely | May not have capacity |
| Peak Season Prep | Stock up for Q4 | Limited Q4 inventory |
If your IPI drops below 400 during the Q2 evaluation period (April-June), storage limits apply for Q3. That means you enter Q4 with restrictions. You can't stock up for Black Friday and holiday sales. This is how low IPI scores cost sellers tens of thousands in lost revenue, not just storage fees.
IPI improvements compound. Fixing excess inventory also improves sell-through rate. Resolving stranded listings immediately removes dead weight. Here are the strategies ordered by impact speed.
Go to Inventory > Fix Stranded Inventory in Seller Central. Resolve every stranded listing today. Common fixes: relist the product, match to an existing ASIN, or create a removal order. Stranded inventory has zero revenue potential but counts against your IPI. Fixing it is the fastest IPI boost because it removes dead weight from the calculation.
Amazon flags ASINs as "excess" when holding costs exceed the expected revenue from selling at current velocity. For each excess ASIN, you have three options: run a Lightning Deal, reduce price by 10-20%, or create a removal order. Running a targeted promotion is usually better than removal because you recover some margin and improve sell-through rate simultaneously.
The arithmetic below is an illustration, not a customer result. Say a quarter of your catalogue is flagged excess. Coupon the twenty highest-volume of those ASINs at 15% and the cost is 15% of whatever revenue those units generate, paid once. Remove the genuinely dead SKUs and the cost is the removal fee per unit, also paid once. Set that against monthly storage on the same units, plus the aged-inventory surcharge that starts compounding, plus the restock capacity you free before Q4. The clear-out is almost always cheaper than holding, and both sides of that comparison are numbers you can pull for your own catalogue in an afternoon.
Days of Inventory (DOI) is the most practical lever for IPI improvement. If your average DOI is 90 days, you're holding twice as much stock as necessary. Reduce restock quantities to target 45-day supply. This simultaneously reduces excess inventory percentage and improves sell-through rate. Two IPI factors improved with one action.
Sort your FBA inventory by units sold in the last 90 days. Any SKU with zero or near-zero sales is dragging your IPI down. Create removal orders for truly dead inventory. The removal fee ($1.04-$1.53/unit) is always cheaper than months of storage fees plus the IPI penalty. Use Nova's Winners & Losers analysis to identify which SKUs aren't earning their shelf space.
For ASINs flagged as excess that still have demand potential, launch a targeted Sponsored Products campaign to accelerate sales velocity. Even a modest increase in daily sales (2-3 extra units) can move an ASIN from "excess" to "healthy" within 2-3 weeks. Track the TACoS impact to ensure the ad spend doesn't exceed the storage fee savings.
While in-stock rate carries less IPI weight, consistent stockouts on your best sellers still hurt. Set up restock alerts for your top 20 revenue-generating ASINs. Use Nova's pipeline projections to ensure inbound shipments arrive before you hit zero units. The goal is never running out on high-velocity products.
Amazon Warehousing and Distribution (AWD) stores bulk inventory outside FBA. Units in AWD don't count against your FBA storage volume or IPI calculations. By keeping 60-90 days of stock in AWD and replenishing FBA with 30-day batches, you improve both IPI and storage costs simultaneously. Read our restock limits guide for more on capacity management.
Nova's FBA inventory tracker shows DOI, demand velocity, and stock position for every ASIN. Color-coded indicators flag excess stock (60+ days), at-risk inventory (under 14 days), and pipeline projections showing when inbound shipments arrive. For the full Amazon inventory management software view, storage fees and aging inventory tie straight into P&L analytics, so you can calculate the true cost of holding inventory vs. Running promotions to clear it.
Amazon evaluates IPI scores during specific windows each quarter. Understanding this timeline lets you plan inventory actions proactively instead of reacting to limit notifications.
| Evaluation Period | IPI Check Window | Limits Applied | Critical For |
|---|---|---|---|
| Q1 (Jan-Mar) | Last 6 weeks of Q1 | Q2 (Apr-Jun) | Summer inventory |
| Q2 (Apr-Jun) | Last 6 weeks of Q2 | Q3 (Jul-Sep) | Q4 prep season |
| Q3 (Jul-Sep) | Last 6 weeks of Q3 | Q4 (Oct-Dec) | Holiday season |
| Q4 (Oct-Dec) | Last 6 weeks of Q4 | Q1 (Jan-Mar) | Post-holiday clearance |
The Q2 check determines your Q3 limits. If you fail, you enter Q4 prep season with restricted capacity. Start cleaning up excess inventory in April, not June. By mid-May, your actions from April start showing in the IPI calculation. Give yourself a full evaluation cycle of clean performance.
Low IPI doesn't just limit your storage capacity. It creates a vicious cycle with storage fees:
The key insight: IPI improvement is a flywheel, not a one-time fix. Once you break into the upward spiral, maintaining a high IPI becomes easier because all four factors reinforce each other. The hard part is the initial cleanup. Focus your first two weeks on stranded inventory and dead SKUs (fastest impact), then shift to DOI optimization for sustained improvement.
Complete breakdown of monthly, seasonal, and aged inventory surcharges.
DOI formula, category benchmarks, and reorder point strategies.
Cash flow strategies, demand forecasting, and reorder systems.
Data-driven framework for deciding which SKUs to keep, kill, or grow.
Join thousands of successful sellers who use Nova Analytics to make data-driven decisions and maximize their profits.
Explore more expert insights to grow your Amazon business
Every FBA storage fee explained: monthly rates, Q4 surcharges, aged inventory penalties, AWD comparison, and 5 strategies to cut costs by 25-40%.
Capacity Manager explained: how limits are calculated, bidding for additional space, and 6 strategies to maximize your FBA storage allocation.
2026 FBA storage fee rates, monthly cost calculator, and long-term storage penalty thresholds. Plus 5 strategies that save sellers $5K-$20K per year. IPI score guide included.
