FBA stands for Fulfilment by Amazon. You send stock to Amazon’s warehouses and, when a customer orders, Amazon picks, packs and ships it, then handles customer service and returns. You pay per-unit fulfilment fees and monthly storage fees, and your listings become Prime eligible.
In warehousing terms it is outsourced fulfilment with one significant difference: your fulfilment provider is also your sales channel, and the two are connected. Using FBA does not just change who packs the boxes — it changes how visible your listings are, which is usually the real reason sellers use it.
How FBA works
You send stock in. Amazon tells you which fulfilment centre to ship to, and the labelling and packaging requirements are specific. Get them wrong and the shipment is refused, delayed, or charged for correction.
Amazon stores it. Your stock sits in their network, often split across multiple sites so it is closer to different customers.
A customer orders. Amazon picks, packs and ships it, usually under their own delivery promise.
Amazon handles the aftermath. Customer service enquiries, delivery problems, returns processing. Returned items are inspected and either put back into sellable stock or set aside.
You get paid, less the fees, on Amazon’s settlement schedule.
The stock remains yours throughout. It is your working capital sitting in someone else’s building, which matters when things go wrong.
What it costs
Three main charges, plus several that surprise people.
Fulfilment fees are per unit shipped, based on the item’s size and weight. This is the biggest and most predictable cost, and it is where product dimensions matter enormously — an item that falls just over a size threshold can cost meaningfully more per unit to ship, and shaving packaging down to stay under a band is a real and worthwhile exercise.
Storage fees are charged monthly per volume of space occupied. They rise sharply in the run-up to peak season, which is a deliberate signal to keep only what will sell.
Long-term storage fees apply to stock sitting beyond a defined period. This is the charge that punishes over-ordering, and it compounds: slow stock costs more to store precisely when it is proving it does not sell.
Removal or disposal fees if you take stock back or have it destroyed.
Returns processing on some categories.
Inbound shipping to Amazon’s chosen sites, which may be several, splitting one consignment into multiple deliveries.
The costs that catch sellers out are almost always storage-related rather than fulfilment-related. Fulfilment fees are visible per sale. Storage fees accumulate quietly against stock that is not selling, which is exactly when you can least afford them.
Why sellers use it
The Prime badge. This is the honest answer. FBA listings carry Prime eligibility, which materially affects conversion and visibility on the platform. For many sellers this alone justifies the fees, regardless of whether Amazon packs boxes better than they would.
The Buy Box. Fulfilment method is one input into which seller wins the Buy Box on a shared listing, and FBA sellers are advantaged.
Scale without infrastructure. No warehouse, no staff, no equipment. A business can go from a spare room to national next-day delivery without a lease.
Peak absorption. Your volume quadrupling in December is Amazon’s problem rather than yours.
Multi-channel fulfilment. You can have Amazon fulfil orders from your own website out of the same stock pool, though at a different rate.
Where it goes wrong
Margin gets thin quietly. Fees change, and a product that was comfortably profitable can stop being so without anything visibly happening. Recalculate per-unit profitability regularly rather than assuming it holds.
You lose control of the customer. Packaging is Amazon’s. The delivery experience is Amazon’s. The customer relationship is largely Amazon’s, and the data about it is not fully yours.
Stranded and unfulfillable inventory. Listing problems, compliance flags or category restrictions can render stock unsellable whilst it continues to accrue storage fees. It is your capital, immobilised, in a building you cannot walk into.
Commingling risk. If you opt into stock being pooled with other sellers’ identical items, you can end up shipping someone else’s unit — and wearing the consequence if it is counterfeit or defective. Most established sellers label individually to avoid this.
Storage limits. Amazon restricts how much you can send based on your sales performance, which can constrain you exactly when you are trying to grow.
Preparation requirements are strict. Polybagging, suffocation warnings, labelling, expiry formatting. Non-compliance means fees or refusal.
FBA vs FBM vs a 3PL
FBM — Fulfilment by Merchant — means you hold the stock and ship it yourself. You keep control, packaging and margin, and you give up the Prime badge unless you qualify for Seller Fulfilled Prime, which carries demanding performance requirements.
A third-party logistics provider sits between the two. Someone else does the warehousing and shipping, but they work for you rather than for the platform, they handle all your channels equally, and your stock is not subject to a marketplace’s storage policies. Usually cheaper than FBA at higher volumes, without the Prime advantage.
A rough guide:
- FBA suits small, light, fast-moving products sold predominantly on Amazon, where the Prime badge drives the sales.
- FBM suits large, heavy, slow-moving or highly customised products, and sellers who want the customer relationship.
- A 3PL suits multi-channel sellers, anyone with significant volume off Amazon, and products that FBA’s size and storage economics punish.
Plenty of sellers run a combination — FBA for the fast lines, a 3PL or self-fulfilment for the bulky and slow ones. That is usually the most economical answer once volumes are meaningful, and it also removes the single-point dependency.
Working out whether FBA pays for a product
The calculation is per product, not per business, and it is worth doing properly because the answer varies enormously across a range.
Start with the per-unit economics:
- Selling price less
- Amazon referral fee (a percentage of sale price, varying by category), less
- FBA fulfilment fee (per unit, by size and weight), less
- Monthly storage cost per unit (storage fee divided by units held, multiplied by how many months they sit), less
- Landed unit cost (product plus inbound freight plus duty), less
- Inbound shipping to Amazon
What remains is contribution per unit. Multiply by expected monthly sales and compare with the same calculation for a 3PL or self-fulfilment.
Two things dominate the result.
Size and weight bands. Fulfilment fees step rather than scale smoothly, so an item a few millimetres over a threshold costs disproportionately more. Reducing packaging to drop a band is one of the highest-return exercises available to an FBA seller, and it is frequently overlooked because the packaging decision was made before anyone looked at the fee table.
Turnover. Storage cost per unit sold depends entirely on how long units sit. A product turning twelve times a year carries roughly a month of storage per unit. One turning twice a year carries six months, plus long-term storage fees, and that alone can erase the margin on a product that looks healthy on fulfilment fees alone.
This is why the same seller can find FBA highly profitable on some lines and loss-making on others. Running the calculation line by line, rather than accepting FBA as a blanket policy, is usually where the money is.
Who FBA is right for
The answer depends less on how big you are than on what kind of seller you are, because the model suits some approaches far better than others.
Private label. The strongest fit. You own the listing, you control the supply, and you are competing on the product rather than on the buy box. FBA gives you Prime eligibility and the conversion lift that comes with it, and because you set the price you can build the fees into it from the start. Most sellers building a brand on Amazon use FBA, and the ones who do not are usually selling something FBA handles badly.
Wholesale and reselling. Also a good fit, with a caveat. You are sharing a listing with other sellers, and FBA offers are heavily favoured for the buy box, so being on FBA is close to a requirement to win sales at all. The caveat is margin: wholesale margins are thinner, so the fee calculation matters more and a slow-moving line can be loss-making after storage.
Retail and online arbitrage. Workable and demanding. The economics rely on buying below the prevailing price and turning stock quickly, and FBA’s per-unit fees plus long-term storage charges punish anything that sits. It also means committing stock to Amazon’s network before you know how fast a one-off buy will sell. Sellers who do this well are disciplined about turnover and about checking fees before every purchase.
Handmade and low-volume makers. Usually not, at least at first. Per-unit fees and inbound shipping are hard to justify on small batches, and if you are making to order there is nothing to send in. Fulfilment by the seller keeps the cost proportional to the sales.
Large, heavy or low-value goods. Rarely. Size and weight drive the fulfilment fee and storage is charged by volume, so a bulky item with a modest price is where FBA economics break down most reliably. Check the fee against the margin before assuming otherwise.
Sellers with fragile, hazardous, temperature-sensitive or heavily regulated products. Check the restrictions before planning around FBA at all. Some categories are excluded outright, others need approval, and finding out after you have bought stock is an expensive lesson.
Sellers who also sell elsewhere. Worth knowing that stock in Amazon’s network can fulfil orders from your own site and other channels through multi-channel fulfilment, at a higher fee. Whether that beats holding stock in two places depends entirely on your split between channels.
A reasonable rule: if your product is small, light, sells steadily, and carries enough margin to absorb the fees, FBA almost certainly pays. If any one of those four is untrue, do the arithmetic properly before committing stock — the calculation in the previous section is the one that settles it.
Preparing stock correctly
Most first shipments go wrong in the same few ways, and the corrections are charged back to you.
- Labelling. Each unit generally needs a scannable barcode, either the manufacturer’s or an Amazon-specific label. It must be clean, flat and not obscured by other barcodes, which frequently means covering the original.
- Polybagging. Items that could be damaged or soiled need bagging, and bags above a certain size need a suffocation warning printed on them.
- Bundles and multipacks must be labelled so they cannot be separated and sold individually by mistake.
- Expiry dates must be printed in the required format and stock must arrive with sufficient remaining life.
- Carton limits. Weight and dimension caps per box, with additional marking for heavier cartons.
- Shipment plans. Amazon determines the destination sites, which may split your consignment, and shipping to the wrong site incurs charges.
None of this is difficult, but all of it is specific, and the rules change. Checking the current requirements before each new product type is faster than resolving a rejected shipment.
Where to go deeper
- What is a 3PL — the independent alternative.
- What is order fulfilment — the process being outsourced.
- What is a fulfilment centre — the kind of building this happens in.
- Inventory turnover — the number that determines whether storage fees hurt.
- Carrying cost of inventory — what holding stock costs you anywhere.
The one-line takeaway
FBA means Amazon stores, picks, packs and ships your stock and handles returns — and the Prime badge it carries is usually the real reason to use it, provided your product size and turnover suit the fee structure.
Frequently asked questions
What does FBA stand for? Fulfilment by Amazon. You send stock to Amazon’s warehouses and they handle storage, picking, packing, shipping, customer service and returns.
How much does FBA cost? Two main charges: a per-unit fulfilment fee based on size and weight, and a monthly storage fee based on volume occupied. Long-term storage fees apply to stock held beyond a set period, and removal, disposal and returns charges may apply. Rates vary by marketplace and change periodically.
Is FBA worth it? For small, light, fast-selling products sold mainly on Amazon, usually yes, because the Prime badge lifts conversion enough to cover the fees. For bulky, heavy or slow-moving products the storage economics often make a 3PL or self-fulfilment cheaper.
What is the difference between FBA and FBM? FBA means Amazon fulfils the order. FBM means you do. FBA gives you Prime eligibility and Buy Box advantage; FBM gives you control over packaging, margin and the customer relationship.
Who owns the stock in FBA? You do. Amazon stores and handles it, but it remains your inventory and your working capital until it sells.
What is stranded inventory? Stock sitting in Amazon’s warehouses that cannot be sold — usually because of a listing error, a compliance issue or a category restriction. It continues to accrue storage fees whilst unsellable, so it is worth monitoring and resolving quickly. Amazon reports it in the seller dashboard, and most cases are fixed by correcting the listing rather than removing the stock.
How long does it take for stock to become sellable? Usually a few days from arrival at the fulfilment centre, though it varies with volume and can stretch considerably around peak. Plan inbound shipments well ahead of the demand you are stocking for, because receiving delays are outside your control.
Can I use FBA for orders from my own website? Yes, through multi-channel fulfilment, which lets Amazon ship orders taken elsewhere from the same stock. Fees differ from standard FBA, and the packaging may carry Amazon branding depending on the option chosen.
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