Amazon FBA Inventory Management: Tips to Avoid Stockouts and Storage Fees

Why FBA Inventory Management Breaks Down

Most FBA sellers run into the same two problems: they run out of stock on fast sellers, or they pay unnecessary storage fees on slow ones. Both destroy margin. Stockouts kill your BSR and hand customers to competitors. Excess inventory racks up long-term storage fees that eat into profit on every unit. The fix is a systematic approach to each of these issues.

IPI Score and Storage Limits

Amazon uses your Inventory Performance Index (IPI) score to decide how much storage space you get at FBA warehouses. The score runs from 0 to 1000. If your IPI drops below 400, Amazon can impose storage volume limits that restrict how many units you can send in. A score above 450 keeps your limits high and gives you the most flexibility.

Your IPI is driven by four factors: excess inventory percentage, sell-through rate, stranded inventory rate, and in-stock rate on your best sellers. Fixing stranded inventory and keeping your sell-through rate healthy will move the needle faster than anything else.

Check your IPI in Seller Central under Inventory, then Inventory Performance. Amazon updates it weekly. If you see it trending down, act before it crosses 400, not after.

Reorder Points: The Formula That Prevents Stockouts

The reorder point tells you exactly when to send a new shipment before you run out. The basic formula is:

Reorder Point = Lead Time x Daily Sales Rate

Lead time is the number of days from when you place a manufacturing or supplier order to when inventory checks in at an FBA warehouse. For domestic suppliers, this might be 7 to 14 days. For overseas production, it can be 60 to 90 days including ocean freight and check-in processing.

Add a safety buffer to account for delays and demand spikes:

Reorder Point = (Lead Time x Daily Sales Rate) + Safety Stock

Safety stock is typically 10 to 20 days of average sales. For high-velocity ASINs or products with long lead times, go higher. For slow movers, keep safety stock lean to avoid paying for idle inventory.

Example: if your lead time is 45 days, you sell 8 units per day, and you want 15 days of safety stock, your reorder point is (45 x 8) + (15 x 8) = 480 units. When your FBA stock drops to 480, place the next order.

Seasonal Inventory Spikes

Seasonal products need separate planning. The mistake most sellers make is ordering based on normal sales velocity and then running out in week two of Q4. For any product that sees a seasonal spike, map your sales history by week for the prior two years and identify the multiplier. If your product normally sells 5 units per day but hits 20 per day in November and December, build that 4x factor into your reorder calculations for the pre-season shipment.

FBA check-in times also slow down during peak periods. Amazon's warehouses are congested in October and November. Build in an extra two to three weeks of buffer for any Q4 shipment to account for slower receiving.

On the other side, products with a clear seasonal drop (outdoor furniture in winter, for example) should have inventory drawn down ahead of the slow season to avoid paying for units that will sit for months.

FBA Storage Fee Tiers

Amazon charges monthly storage fees based on the cubic footage your inventory occupies. Fees are higher in Q4 (October through December) than in Q1 through Q3. In 2026, standard-size products cost approximately /usr/bin/bash.78 per cubic foot per month in the off-peak period and .40 per cubic foot per month during Q4.

Long-term storage fees apply to units that have been at an FBA warehouse for more than 365 days. These fees are charged on top of monthly storage. For most products, holding a unit for over a year at FBA is not economical. If you have aged inventory, run a removal order or create a deep discount to liquidate it before the long-term threshold hits.

To see which ASINs are costing the most in storage, go to Inventory, then Inventory Age in Seller Central. Sort by estimated storage cost and tackle the highest-cost items first.

Stranded Inventory: Find It and Fix It Fast

Stranded inventory is stock sitting at an FBA warehouse with no active listing. You are paying storage fees on units that cannot sell. Common causes: a listing was deleted, the product was suppressed, or there was an attribute mismatch between the listing and the fulfillable unit.

In Seller Central, go to Inventory then Fix Stranded Inventory. Amazon shows every stranded ASIN with a reason code. Most fixes take minutes: relist the product, match the condition, or correct the FNSKU mismatch. Do not let stranded inventory sit. Check this tab at least weekly.

Tools That Make FBA Inventory Management Easier

Doing all of this manually across dozens or hundreds of ASINs is not scalable. These three tools handle the heavy lifting:

• InventoryLab: Combines inventory management with profit and loss tracking. It pulls your FBA data and shows you actual per-unit profitability after fees. Good for sellers who want financial detail alongside reorder alerts.
• SoStocked: Built specifically for Amazon FBA reorder planning. It calculates reorder points automatically based on your lead times and daily sales, flags products that need restocking, and lets you build seasonal multipliers into your forecasts. Strong choice for sellers with complex multi-supplier setups.
• RestockPro: Focused on reorder recommendations and shipment building. It integrates directly with Seller Central to pull live inventory levels and sales velocity, then generates restocking recommendations. Straightforward interface and easy to set up.

Any of these tools will pay for itself quickly if it catches even one major stockout or prevents a round of long-term storage fees.

The Weekly Inventory Review

Build a short weekly review into your process. Check IPI trajectory, review stranded inventory, compare current stock against your reorder points, and look at the Inventory Age report for units approaching 365 days. Thirty minutes per week prevents most of the problems that cost FBA sellers money. Inventory issues do not appear suddenly; they build slowly over weeks. Catching them early keeps both stockouts and storage fees under control.