FBA capacity limits: what they are, how Amazon sets them and how to plan around them

FBA capacity limits decide how much of your inventory Amazon will hold at any one time. On March 1, 2023, Amazon replaced weekly restock limits and quarterly storage limits with a single monthly limit per storage type, measured in cubic feet. The storage types are standard-size, oversize, extra-large, apparel and footwear, each with its own limit, and Amazon says capacity cannot be moved from one type to another. Capacity for dangerous goods, such as flammables and aerosols, is handled separately. The rules here come from Amazon's US seller pages and forum posts; other marketplaces can differ.

How is FBA capacity usage calculated?

Amazon sets the limit. Your job is to track usage against it. Usage counts two things: stock already sitting in fulfillment centers, and open shipments, which count from the day you create them, not the day they arrive.

Capacity used = on-hand volume + open inbound volume (cubic feet, per storage type)

Headroom = monthly limit − capacity used

Unit volume = length × width × height in inches ÷ 1,728 (cubic inches in a cubic foot)

Take a standard-size limit of 1,500 cubic feet, with 900 on hand and 350 in open shipments. Headroom is 250 cubic feet. What that buys depends on the product:

SKU	Packaged size (in)	Cubic feet per unit	Units that fit in 250 cu ft
A	12 × 9 × 4	0.25	1,000
B	18 × 14 × 8	1.17	214

Same headroom, nearly five times the units for the smaller SKU. That is why a replenishment plan written in units can be impossible to ship.

How does Amazon set your limit?

An Amazon staff post splits accounts three ways:

• Individual accounts: fixed at 15 cubic feet, not eligible for increases.
• Professional accounts active in FBA for less than 39 weeks: no capacity limits.
• Professional accounts active in FBA for 39 weeks or more: limits based on IPI and sales performance.

For those established accounts, Amazon's help page says the limit is shaped by your IPI score along with historical sales, seasonal peaks, forecasts for your ASINs, new selection, scheduled deals, shipment lead time and its own fulfillment center capacity. The staff post says a consistently strong IPI earns more space, scaled to how much you sell and how much room Amazon has.

You see the limit and your usage in Capacity Monitor at the bottom of the FBA dashboard, with a tab for each storage type and a table of limits for the next three months. Limits are typically announced in the fourth week of the month, in Capacity Monitor and by email: the coming month's limit is confirmed, the next month's estimate is reaffirmed or adjusted, and a new estimate is added for the month after. If you need more room, Capacity Manager lets you ask for extra space and name the most you will pay as a reservation fee. Amazon reviews free space about twice a week and fills requests from the highest bid per cubic foot down. Performance credits earned from your sales can offset the fee.

Why do capacity limits matter for operations and growth?

Capacity is a shared budget. Every SKU in a storage type competes for the same cubic feet, so one slow, bulky SKU can crowd out a best seller that is about to run out. Amazon blocks new shipments once on-hand stock plus open shipments exceeds the limit, and blocks any shipment whose units would push you over it, so new inbound for that storage type waits until space frees up.

Fees are a moving target. Amazon's 2023 rules charged an overage fee when on-hand stock alone ran over the limit, then in 2024 Amazon said it had dropped that fee from July 1, 2024. Check the current fee pages before you plan to run over.

The limit also looks forward. Because IPI is an input, inventory that sits unsold today can mean less space next month. And a launch or seasonal push that needs extra stock has to be planned against the estimated limit, not this month's.

What mistakes do sellers make with FBA capacity?

• Planning in units. Limits are in cubic feet. Convert every SKU before deciding quantities.
• Forgetting open shipments. Shipments count from the moment you create them. Stale or oversized shipments you never send still hold space.
• Treating storage types as one pool. Headroom in standard-size does nothing for an oversize SKU.
• Using FBA as the warehouse. Amazon says AWD inventory does not count against FBA storage limits, and AWD can replenish FBA automatically. A 3PL can hold buffer stock too.
• Checking the limit once a month. Headroom moves every day as units sell, customer returns are received, removal orders are created (usage drops within 24 hours, even while pending) and shipments are created or cancelled.

How does Growth OS plan around capacity limits?

Ecomsellertool Growth OS runs on your own accounts and is built to keep a daily capacity ledger per storage type:

1. Usage. It pulls on-hand and inbound quantities from the SP-API FBA Inventory API, then converts them to cubic feet and groups them using the item volume and storage type Amazon reports for each SKU in the Manage Inventory Health report. Amazon's measurements, not your catalog's, decide usage.
2. Limits. The confirmed limit and the estimates from Capacity Monitor are entered or imported into the ledger when Amazon publishes them, so headroom is known before a shipment is planned.
3. Allocation. When space is tight, it ranks SKUs by days of cover and margin and gives headroom to the ones closest to a stockout.
4. Overflow. Units that do not fit stay in AWD or a 3PL as safety stock, and FBA inbound plans are drafted through the Fulfillment Inbound API (v2024-03-20) for approval.

The full planning logic is in automated replenishment, and the downstream risk is covered in stockouts.

Where should you start?

If capacity surprises you each month, or shipments get planned in units and cut back later, start with the free Quick Scan in the Ops Gap Diagnostic. It works from reports you upload, including an Inventory Ledger or Manage FBA Inventory report, and returns your top three Amazon operations gaps, each with a yearly dollar estimate. The paid Deep Diagnostic covers every channel you sell on. To see the base system first, look at Growth OS.