Amazon FBA Capacity Limits: How Monthly Storage Allocations Work, What Sets Your Number, and How to Use the Capacity Manager

Amazon's capacity limit system has gone through its most disruptive overhaul in years, and sellers who were not paying close attention absorbed the consequences before they could plan around them. Understanding how monthly allocations work, what determines your number, and how to use every available tool is now a core part of running a profitable FBA business - and it directly shapes how you time inbound shipments from your prep center.

Why the System Changed and Why the New Numbers Are Permanent

Amazon moved from quarterly storage limits to a permanent monthly capacity limit model effective January 1, 2026. Then, in May 2025, Amazon reduced the capacity baseline by cutting the projection period it uses to calculate your allocation. Many established sellers - including those with strong IPI scores - lost a substantial portion of their available cubic feet overnight. Amazon has since confirmed the reduced allocations will not be reversed.

The timing caught sellers off guard because the reduction was not a penalty for poor performance. It was a structural reset applied across the board. Accounts that had operated with comfortable headroom for years found their confirmed limits far below their typical inbound volume. The change reflects Amazon's shift toward tighter matching of FC capacity to actual consumer demand, but the operational effect on sellers is straightforward: you have less room, permanently.

Monthly limits also close the recovery window. Under the quarterly model, a seller who overbuilt in month one had two more months to sell down inventory before the next allocation reset. Monthly limits reset every 30 days, so an oversized shipment plan sent without checking the confirmed limit carries no buffer.

The Seven Storage Types and Why You Cannot Swap Cubic Feet Between Them

Amazon assigns capacity limits across seven completely separate pools. Unused cubic feet in one type cannot offset a shortfall in another - there is no transfer mechanism.

• Standard-size
• Oversize
• Extra-large
• Apparel
• Footwear
• Aerosol
• Flammable

Extra-large is its own pool, distinct from oversize. Amazon defines extra-large by weight and dimensional thresholds published in its size tier documentation - check Seller Central for the current figures, since a product's classification directly determines which capacity pool it draws from.

The aerosol and flammable pools are walled off for a structural reason that has nothing to do with policy preference. Products classified as aerosol or flammable are physically routed to dedicated fulfillment centers that are separate buildings from standard FCs. Amazon cannot pool cubic feet across physically separate facilities. For a brand that sells both a flammable item and a standard-size item, this means managing three or more entirely independent capacity pools at once. Running out of space in the flammable pool while your standard-size pool still has headroom provides no relief - those cubic feet simply cannot move.

How Amazon Calculates Your Monthly Number

Your monthly capacity limit is calculated from four inputs: IPI score, 90-day sales velocity, seasonal adjustments, and physical available space at fulfillment centers serving your inventory. Sellers can directly influence the first two.

IPI Score Thresholds

The IPI score functions as both a gate and a multiplier. Amazon currently applies two thresholds - check Seller Central for the current figures, as Amazon has adjusted these thresholds before. Sellers above the higher threshold receive unlimited standard-size storage and face no allocation cap on that type. Sellers below the lower threshold face a reduction across all storage types regardless of sales velocity. Sellers in between operate under a calculated limit derived from projected sales.

The Projected-Sales Formula

Amazon estimates your sell-through rate using the prior 90 days and projects it forward across a multi-month window to determine how many cubic feet your inventory would require. Seasonal adjustments layer on top - a seller whose 90-day window captures a holiday surge may receive a larger allocation than a seller with flat sales even if their long-run unit volumes are similar. Check Seller Central for the current projection period, as this formula is a policy setting Amazon has changed and could change again.

The variables sellers can actually influence:

• IPI score - driven by excess inventory percentage, stranded inventory rate, FBA sell-through rate, and in-stock rate
• 90-day sales velocity - consistent sales produce a more generous allocation than spiky or declining sales patterns
• Inventory age - aging stock suppresses IPI without contributing to velocity
• Stranded inventory - units in a stranded state hurt IPI while generating zero sales

Reading the Capacity Monitor: the Three-Month Outlook

Amazon releases capacity information on a fixed calendar. During the third full week of the prior month, Amazon publishes the confirmed capacity limit for the upcoming month via the Capacity Monitor in Seller Central and by email. At the same time, two estimated limits for the following two months are released - verify the current announcement schedule in Seller Central, as timing details may shift.

The confirmed limit is the number you plan to. Estimated limits are useful for identifying structural trends. If both estimates run lower than your current confirmed limit, you are likely moving into a period of tighter allocation and should adjust inbound volume before the next confirmation arrives.

For prep center operations, this three-month window creates a planning rhythm. When the confirmed limit lands in the third week of the month, compare it against shipments currently being prepared and those scheduled to leave your prep center in the coming weeks. If the confirmed limit is below your anticipated inbound volume, you have roughly two to three weeks to adjust - pull back shipment plans, delay sends, or submit a Capacity Manager request before the new month starts.

The Storage Utilization Surcharge: the Hidden Cost of Long-Dwell Inventory

In July 2024, Amazon replaced inventory storage overage fees with a storage utilization surcharge. The mechanics are meaningfully different from the old system and carry a larger cost for sellers holding slow-moving stock.

The surcharge is tiered by inventory age. Standard-size items begin accruing surcharges after they have sat in an FC for an extended period, with the rate stepping up at each age tier through the one-year mark and beyond. Oversize follows the same tier structure but with different rates. Check Seller Central for current per-cubic-foot figures at each tier, since these rates are policy settings Amazon can adjust.

The practical consequence is that the visible monthly storage fee line understates the true cost of slow-moving inventory. A unit that takes eight months to sell does not cost only its base storage fee for those eight months - it accumulates the base fee plus an escalating surcharge for every billing period it sits in late-dwell tiers. For low-margin products with slow turns, the combined cost can eliminate profitability before you notice it on the fee report.

Using the Capacity Manager: the Uniform-Price Auction Most Sellers Misunderstand

When your confirmed capacity limit is not enough, the Capacity Manager lets you request additional space for a specific storage type in a specific calendar month. Each request is scoped to exactly one storage type and one month - a seller managing both standard-size and apparel inventory who needs more of both must submit separate requests for each type.

You submit a reservation fee bid - the amount per cubic foot per month you are willing to pay for the additional space. Amazon reviews all requests every few days, approves them from highest bid down until available capacity is exhausted, then charges all approved sellers the same rate: the lowest bid that was accepted.

This is a uniform-price auction, not a pay-your-bid auction. Every approved seller pays the same clearing price - the lowest accepted bid. Bidding higher than you need to improves your odds of approval when competition is tight, but it does not increase your cost if you are approved.

The reservation fee is not the net cost. Amazon issues performance credits against reservation fees based on how well you use the additional space to generate sales. High-velocity sellers who genuinely need the space - and move inventory through it - regularly reduce or eliminate their net fee through credits. The per-cubic-foot credit rate and current mechanics are published in Seller Central; verify those figures before bidding, but the pattern is consistent: sellers who use the space productively find the net cost is far lower than the headline fee rate suggests.

The Capacity Manager makes most sense when you need to respond quickly to a shortfall in the current month. For building out sustained buffer stock across months, AWD is a better structural solution.

AWD as a Capacity Bypass: the Buffer-Stock Model

Amazon Warehousing and Distribution inventory does not count toward FBA capacity limits. This is the structural bypass for sellers whose sales velocity justifies more stock than their FBA allocation allows.

The model works by separating your working inventory from your buffer inventory. Buffer stock sits at AWD, outside your FBA limit. Auto-replenishment moves units from AWD into FBA as FBA stock depletes. The FBA pool holds only the active working portion of your inventory - the days of stock needed to cover sales between replenishment cycles - rather than months of safety stock. This can substantially reduce the cubic feet your product consumes inside the FBA network. Check AWD program documentation for Amazon's current recommended holding levels at each tier, since these are policy parameters that may be updated.

AWD works best for products with predictable, steady sales velocity. Auto-replenishment cannot respond to demand spikes faster than its replenishment lag allows - so a product with extreme week-to-week variability may still require a larger FBA buffer than the AWD model recommends. For stable, high-volume products, the cubic-foot savings against your FBA limit can be significant.

New Seller Considerations: the Grace Period

New professional selling accounts that are active in FBA for fewer than a certain number of weeks receive no capacity limits regardless of sales volume. Amazon publishes the current duration of this grace period in its new seller policies - verify the figure in Seller Central, as it is a program parameter that can change. During this window, new sellers can ship without restriction, which gives them time to build a sales baseline before Amazon assigns a permanent allocation.

This window matters more than most new sellers realize. Your first confirmed allocation after the grace period ends is anchored to the sales velocity and IPI score you built during it. A seller who maintains consistent inventory, resolves stranded inventory promptly, avoids building aged stock, and keeps FBA actively replenished exits the grace period with a much stronger allocation anchor than a seller who used the window as free warehousing without focusing on sell-through.

Coordinating Inbound Shipments from Your Prep Center Around the Monthly Cycle

The monthly announcement calendar creates a predictable rhythm that sellers and prep centers can plan around together. The most common prep-related capacity mistake is treating inbound planning as a single workflow regardless of storage type. A seller with both standard-size and apparel products needs two separate pipelines, each sized to its own confirmed limit.

1. In the third week of each month, pull the confirmed capacity limit for the upcoming month and compare it against all open and planned shipment plans for that month across every storage type you use.
2. Check the estimated limits for months two and three of the Capacity Monitor outlook and flag any month where estimates are materially below your typical send rate.
3. By the fourth week of the month, finalize which shipments will leave your prep center before the new month begins and which should be held or reduced.
4. For any storage type where the confirmed limit falls short of your anticipated inbound, decide before the month starts whether to submit a Capacity Manager bid, reduce inbound volume, or divert product to AWD bulk storage.
5. Create separate shipment plans for each storage type so your prep center can label and pack them correctly and so you have independent visibility into which allocation each shipment draws from.
6. Before the new month goes live, confirm that no open shipment plan - including any still being processed at the prep center - will push any single storage type over its confirmed limit.

Strategy	Best suited for	Response speed	FBA cubic-foot consumption
Direct FBA send from prep center	Fast-moving, promotionally driven inventory	Same-week shipment possible	Higher - full buffer at FBA
Capacity Manager bid	Short-term shortfall in a specific month	Days, reviewed on a rolling basis	Moderate - limited expansion only
AWD buffer with auto-replenishment	Steady-velocity products with predictable demand	Slower - replenishment lag applies	Lower - bulk stays outside FBA limits
AWD plus Capacity Manager combined	High-volume sellers managing limits across multiple storage types	Moderate	Lowest overall FBA consumption

Frequently Asked Questions

What happens if my IPI score drops significantly after my confirmed limit is already set for the month?

Your confirmed limit for the active month is fixed once Amazon publishes it - an IPI drop during the month does not revise a limit that has already been issued. The damage shows up in the following cycle: the lower score feeds into the calculation Amazon runs when generating estimated and confirmed limits for subsequent months. This makes a mid-month IPI drop particularly costly if it persists long enough to be reflected in the 90-day window when the next allocation is calculated. Resolving the underlying driver - excess inventory, stranded listings, low sell-through rate - quickly after a drop limits how many allocation cycles the lower score affects.

What happens if I win a Capacity Manager bid but do not end up using all the space I requested?

The reservation fee applies regardless of whether you fill the additional space. Performance credits are tied to how well you convert the additional cubic feet into sales - if you request space and then do not send inventory to fill it, you generate little or no credit and pay closer to the full reservation fee. Capacity Manager bids should be sized to inventory you have ready to ship and sell, not as speculative headroom. An undersized shipment against an oversized bid costs the reservation fee on unused space without generating the credits that would reduce your net cost. Check Seller Central for the current credit structure before sizing any bid.

Can I use one shipment plan for products that fall into different storage types?

Maintaining separate shipment plans per storage type is the cleaner approach when you are managing against multiple confirmed limits. Mixing types in a single plan makes it harder to track which allocation is being consumed and easier to accidentally exceed the limit for one type while staying under another. Your prep center also needs clear labeling instructions by storage type to ensure product is routed correctly when it arrives at the FC.

When AWD auto-replenishment moves units into FBA, at what point do those units count against my confirmed limit?

Units count against your FBA capacity limit once Amazon receives them into the FBA network - not when they leave AWD. A replenishment transfer that is in transit but not yet received at an FBA fulfillment center does not appear against your limit yet. Sellers working close to their confirmed limit should treat in-transit AWD-to-FBA transfers as pending drawdowns against available space and account for them in their planning. Checking Seller Central's shipment status alongside the Capacity Monitor - rather than the Capacity Monitor alone - gives the most accurate picture of how much headroom actually remains.

What happens if my shipment arrives at Amazon and I am over my confirmed limit for that storage type?

Amazon will not simply receive overage inventory at no cost. Shipment plans that exceed your confirmed limit may be rejected at the plan creation stage or flagged on arrival, and the storage utilization surcharge structure means any inventory that does get received and then sits aging will cost progressively more per cubic foot the longer it stays. The safest approach is to resolve the gap - through a Capacity Manager request, a delayed send, or an AWD diversion - before the shipment leaves your prep center.

What allocation can I expect for a storage type where I have no prior sales history?

If you are an established seller launching a product in a storage type you have never used before - for example, adding an aerosol item to an account that has only ever used standard-size inventory - Amazon has no 90-day velocity data to project from for that pool. Initial allocations for a storage type with no history are typically minimal. The practical consequence is that a new storage type requires the same kind of baseline-building that new sellers face after their grace period ends: small initial sends, consistent sell-through, and time before the projection window holds enough data to support a meaningful allocation. Planning a large launch in an unfamiliar storage type without accounting for this cold-start constraint is a consistent source of unexpected capacity shortfalls.