Amazon FBA vs FBM: which is right for your product?

What each one actually means

• FBA (Fulfilled by Amazon). You ship inventory to Amazon. They store it, pick it, pack it, deliver it, and handle returns and customer service. Your listings get the Prime badge.
• FBM (Fulfilled by Merchant). You hold the stock and ship each order yourself, or through a third-party warehouse. You handle delivery times, returns and customer messages.

The cost comparison nobody shows you

Here is a worked example on a 1.8 lb kitchen product at $28.99, using 2026 fee figures:

FBA wins by $2.46 a unit here — and that comparison already excludes the rent, utilities and software FBM needs. For a mid-weight, fast-moving product, FBA is usually not just easier, it is cheaper.

Change the product and the answer flips entirely.

The threshold that decides it

That threshold is really a proxy for weight and speed. FBA fulfilment on a sub-1 lb item runs around $3.22–$3.86. On something over 20 lb it can reach $20 and, on genuinely oversized items, far more. Meanwhile the referral fee is identical either way, so the whole decision rests on fulfilment, storage and your own labour.

When FBA is the right answer

• Small and light. Under about 1 lb, where fulfilment fees are low enough that doing it yourself saves little.
• Fast-moving. Inventory that clears in 30–60 days, so storage fees stay negligible. Long-term storage on aged inventory is punitive.
• High volume. Per-unit fees stay flat as you scale, while your own warehouse costs do not.
• Prime-sensitive categories. Where shoppers filter by Prime, not having the badge removes you from the comparison entirely.
• You are new. FBA removes an entire operational discipline you would otherwise have to learn while also learning the marketplace.

When FBM is the right answer

• Heavy or oversized. Above about 20 lb, FBA fees frequently exceed 30–40% of the sale price. That is your entire margin.
• Slow-moving. Under roughly 10 units a month, storage and aged-inventory fees quietly eat the product.
• You already have a warehouse. If the space and staff exist and are not fully used, the marginal cost of shipping an order yourself is small.
• Fragile, custom or branded packaging. Amazon handles your product the same way it handles everything else. If presentation is part of what you sell, that matters.
• High-ticket, low-volume items where one FBA fee is larger than a day of your own labour.

What FBM genuinely costs you

The Buy Box. Published comparisons put FBA’s Buy Box win rate roughly 25–30% higher, and sellers moving an established product from FBA to FBM commonly report a 15–30% conversion drop at first. Some of that recovers; not all of it does.

That is the trade. FBM can save you several dollars a unit and cost you a fifth of your conversion rate. On a thin-margin product that is a bad deal. On a heavy product where FBA was taking 35% of the price, it is an easy one.

Seller Fulfilled Prime: check before you plan around it

SFP lets you keep the Prime badge while fulfilling yourself. The requirements are demanding — around 99% on-time delivery, cancellation and tracking defect rates under 0.5%, nearly all orders delivered in one or two days, and weekend fulfilment — with automatic removal if you slip.

The programme’s availability has changed more than once. Check its current status directly in Seller Central before building a fulfilment strategy on it.

The answer most sellers land on

A split. FBA for the light, fast-moving SKUs where the fees are small and the Prime badge does the heavy lifting. FBM for the heavy, slow or bulky items where FBA fees would take the margin.

Work it out per SKU. Take your FBA fees as a percentage of selling price, sort the catalogue by that number, and look hard at everything above 25%. The answer will usually be sitting right there.