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Amazon FBA Inventory Management and Restock Limits

Restock limits became monthly FBA capacity limits in 2023. How the limits work, what the IPI score changes, and the math for planning shipments that fit your space and keep you in stock.

By Invechar Team. Updated . 8 min read

If you sell through Fulfillment by Amazon, you manage two inventories at once: the stock in your own hands and the stock inside Amazon's network. The second one has rules you do not control. Amazon decides how much space you get, charges more when stock sits too long or runs too low, and can block new shipments when you exceed your limit.

This guide explains how those limits work today, where restock limits went, and how to plan FBA shipments so they fit your space and keep you in stock.

In short: Amazon replaced weekly restock limits and storage limits with one monthly FBA capacity limit in March 2023, measured in cubic feet and covering stock on hand plus shipments on the way. Plan in cubic feet, protect your best sellers first, keep your Inventory Performance Index healthy and check the Capacity Monitor every month.

Restock Limits Became Capacity Limits

Sellers who learned FBA before 2023 remember restock limits: caps on how many units of each storage type you could send. In its own announcement, Amazon introduced a streamlined capacity management system that took effect on March 1, 2023. It replaced the separate restock and storage limits with a single monthly FBA capacity limit.

The key points from Amazon's announcement and its follow up guidance:

  • The limit is monthly and expressed in cubic feet, per storage type.
  • Usage counts inventory on hand at Amazon plus open shipments on the way to fulfillment centers.
  • Amazon publishes the confirmed limit for the coming month and estimates for the two months after it, so you can plan ahead. Estimates can move up or down.
  • You see all of this in the Capacity Monitor in Seller Central.
  • If inventory on hand plus open shipments would exceed your limit, you are blocked from creating new shipments for that storage type. Amazon dropped the separate capacity overage fee in August 2024, backdated to July 1, but the shipment block still applies.

Amazon has also said that new professional selling accounts start without capacity limits while they build a sales history in FBA, and that individual selling accounts have a small fixed limit. Amazon changes these details from time to time, so treat your own Capacity Monitor as the source of truth.

How Your Limit Is Set

Amazon sets limits from a mix of your sales performance, your Inventory Performance Index (IPI) and how much space and labor its network has available. Two things follow:

  1. Selling through stock raises your ceiling. Sellers who turn inventory efficiently tend to get more room.
  2. The network matters. When Amazon's own space and labor are tight, limits can change even if your performance has not, so plan with the estimates and keep a margin.

Capacity Manager

If your limit is too low for a plan you are confident in, Capacity Manager lets you request more capacity by naming a reservation fee you are willing to pay. Amazon grants requests from its available space, and the fee can be offset by performance credits earned from sales of the added inventory. Bid only for space you are sure to sell through; unsold stock in reserved space costs you twice.

The Inventory Performance Index

Amazon's help page describes the IPI as a measure of how efficiently and productively you manage FBA inventory over time, and it points to the actions that matter most:

  • Balance stock with sales. Do not send far more than you sell.
  • Reduce excess and aged inventory that is not selling.
  • Fix listing problems that leave stock unsellable, such as stranded units with no active offer.
  • Keep popular products in stock.

You find your score under Inventory planning in Seller Central. Amazon does not publish the exact formula, and third party claims about "safe" thresholds vary, so watch your own trend and the recommendations Amazon shows you rather than chasing a number.

Plan FBA Inventory in Cubic Feet

Units are how you sell; cubic feet are how Amazon allocates space. Plan in both.

Step 1: Work Out Space per Unit

Use the packaged dimensions of one unit in inches:

Cubic feet per unit = (Length x Width x Height in inches) / 1,728

A product packed in a 10 x 8 x 4 inch box takes 320 / 1,728 = 0.185 cubic feet.

Step 2: Decide How Many Days of Cover to Hold at Amazon

Days of cover at Amazon has to bridge the time until your next shipment is received and available, not just delivered:

Target days of cover = Days until the next shipment is available + Safety days

Include the time to prepare and ship from your warehouse and Amazon's receiving time, which you should measure from your own past shipments. Receiving tends to slow before peak season.

Step 3: Work Out the Shipment

Units to send = (Target days of cover x Average daily units sold) - (FBA available + FBA inbound)
Space needed = Units to send x Cubic feet per unit

A Worked Example

A product sells 20 units a day. Your next shipment after this one will be available in 35 days, and you want 10 safety days, so the target is 45 days of cover, or 900 units. Amazon holds 380 units and 120 are inbound. You need 900 minus 500, or 400 units, which at 0.185 cubic feet each is 74 cubic feet. Check that against the room left in your Capacity Monitor for that storage type before you create the shipment.

Try it on your own data: start free, no card needed.

When Space Is Tight, Rank by Profit per Cubic Foot

When capacity will not fit every plan, do not cut every product evenly. Give space to the products that earn the most from it:

Monthly profit per cubic foot = (Profit per unit x Units sold per month) / (Average units stored x Cubic feet per unit)

A small, fast seller can earn many times more per cubic foot than a bulky slow one. Protect the top of that list first, keep the slow and bulky products lean at Amazon, and hold their extra stock in your own warehouse or a lower cost storage option until they are needed.

Fees That Respond to Stock Levels

Amazon's FBA fees reward balanced stock. Monthly storage costs more in the last quarter of the year, older stock can attract an aged inventory surcharge, and in 2024 Amazon introduced a low-inventory-level fee for products whose stock is low compared with their sales. The thresholds and rates change regularly, sometimes more than once a year, so check Amazon's current fee pages in Seller Central before you plan around them. The practical rule holds either way: send enough to stay comfortably in stock, and not so much that it ages.

Inbound Problems That Waste Capacity

Open shipments count against your capacity from the moment you create them, so anything that slows or breaks an inbound shipment costs you space as well as time:

  • Shipments created but not sent. Cancel plans you will not ship; they hold capacity you could use for something else.
  • Slow receiving. Stock that is delivered but still being received counts as usage and cannot sell. Ship earlier ahead of peak periods, when receiving tends to take longer.
  • Prep and labeling errors. Units that need extra prep or relabeling at the fulfillment center can be delayed or charged for. Follow Amazon's prep requirements for each product.
  • Quantity discrepancies. If Amazon receives fewer units than you sent, check the shipment in Seller Central, provide proof of what was shipped and raise a reconciliation where you are owed one. Unclaimed shortages are lost margin.

Track each shipment from creation to fully received, and compare received quantities line by line with what you packed.

Keep, Remove or Liquidate

Space at Amazon is limited and storage charges rise with age, so slow stock should earn its place:

Keep at Amazon if: Expected profit from units sold in the next 90 days > Storage and aged inventory charges over the same 90 days

If a product fails that test, compare the options: lower the price to sell through, run a promotion, remove the units to your own warehouse to sell on other channels, or liquidate. Removal has its own fee, and stock you bring home can still be sold on eBay, Shopify or wholesale, which often makes it the better choice for products that sell elsewhere.

Amazon Warehousing and Distribution as a Buffer

Amazon Warehousing and Distribution (AWD) is Amazon's bulk storage service upstream of FBA. Amazon describes it as low cost bulk storage that can replenish your FBA inventory automatically, using its own model of your demand. Amazon's help page says inventory replenished automatically from AWD to FBA is exempt from FBA capacity limits, and that you can opt individual SKUs out of auto-replenishment if you prefer to time shipments yourself. AWD has its own storage, processing and transport fees, so compare it with holding stock in your own warehouse or a 3PL.

Keep FBA Stock Separate from Your Other Channels

Units inside Amazon's network can only fill Amazon orders, or orders Amazon fulfills for you through Multi-Channel Fulfillment. In your inventory system, treat the FBA location as its own pool that never counts as available for eBay, Shopify or wholesale orders you ship yourself. Mixing the two is one of the most common causes of overselling.

A Monthly FBA Inventory Routine

  • Read the Capacity Monitor when the new month's limit and estimates appear, and note the room per storage type.
  • Recalculate target days of cover per product from current sales, not last quarter's.
  • Rank products by profit per cubic foot and decide what gets space first.
  • Draft shipments in cubic feet and confirm they fit before creating them.
  • Review excess and aged stock at Amazon and plan promotions, removals or price changes before surcharges apply.
  • Fix stranded inventory and listing issues that leave units unsellable.
  • Check your IPI trend and Amazon's recommendations.
  • Before peak season, book space early and plan the last shipments that can arrive in time.

Common Mistakes

  • Planning in units only. Two products with the same units can need very different space.
  • Using delivery dates instead of availability dates. Stock in receiving cannot sell.
  • Sending everything at once. Big shipments that sit for months hurt your IPI and attract aged inventory charges.
  • Letting stranded units sit. They use space and earn nothing. Fix the listing or remove them.
  • Counting FBA stock as available everywhere. It cannot ship to your other channels' buyers.

How Invechar Helps

Invechar forecasts demand per product from your own sales trend, learns each supplier's real lead time from received purchase orders, adds safety stock for volatile products and proposes restocks you can edit before approving. Your Amazon FBA stock lives in its own location that never counts as sellable on your other channels. Money Finder and Listing Guard watch for stranded stock, suppressions and units Amazon may owe you for. FBA inbound shipments run in simulated mode until Invechar's Amazon inbound access is approved, so for now you plan the shipment in Invechar and create it in Seller Central.

Read more about restocking and the Restock Planner, FBA shipments and connecting Amazon, or work out your numbers with the reorder point and safety stock guide.

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