Free tool
FBA vs FBM calculator: the same product, two ways to fulfil it
Most FBA vs FBM comparisons stop at the fulfilment fee, which is the smallest part of the difference. Enter your own figures and see both routes side by side: profit per unit, margin, the monthly gap, and the exact volume at which FBM overtakes FBA once its fixed costs are spread across orders.
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Amazon sellers deciding how to fulfil
FBA vs FBM Calculator
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The product, either way
These figures are identical for both routes, which is the point: only fulfilment changes.
Fulfilled by Amazon
Amazon stores, picks, packs and ships. You pay per unit and per month of storage.
Fulfilled by merchant
You or a 3PL ships it. You pay outbound shipping, the packing work and the return leg.
Fees change. This calculator deliberately does not hardcode Amazon's fee table or a carrier's rate card.
FBA profit / unit
$11.31
34.4% margin
FBM profit / unit
$10.85
33.0% margin
Cheaper route
FBA
$0.46 per unit ahead
Monthly gap
$138.60
in favour of FBA at 300 units/month
FBA's lead survives roughly 1.2 more months of storage at $0.40 per unit per month. Slow-selling stock is the most common reason an FBA model stops working.
Where the money goes
Same product, same revenue. Only the cost lines differ.
FBA only
FBM only
Deliberately excluded: the Prime badge, which lifts conversion on FBA listings by an amount that varies by category and cannot be measured from outside an account. Use the gap above as the price of that advantage, not as the whole decision.
What this works out
- Profit per unit and margin for FBA and FBM from the same price and product cost
- The storage months at which sitting inventory makes FBA the more expensive route
- Return shipping, which FBM pays and FBA usually does not, priced per returned unit
- The crossover volume: the monthly order count where FBM's fixed cost is absorbed
- A per-unit cost breakdown for each route, so you can see which line decided it
If the result raises a question you would rather not answer alone, the related services below are the parts of the business this tool usually points at. There is no obligation attached to any of it.
Questions about this tool
What is the actual difference between FBA and FBM?
Under FBA, Amazon stores the stock, picks, packs and ships it, and handles customer service for the order. You pay a fulfilment fee per unit plus storage. Under FBM, you or a third-party warehouse does that work, so you pay shipping, packaging and labour instead, and you keep control of the packing and the timing. The referral fee is the same either way, and that is why comparing only the fulfilment fee gives the wrong answer.
Why does this calculator ask for my fees instead of looking them up?
Because Amazon changes its fee schedule, and a calculator with a hardcoded table becomes confidently wrong the moment it changes. Enter the fulfilment fee and storage rate from the Revenue Calculator in Seller Central, and the shipping rate from your own carrier account. The arithmetic is then yours, not our estimate of yours.
Does it account for the Prime badge?
No, and that is deliberate. FBA listings carry Prime, which usually converts better than an FBM listing on the same product, but the size of that effect depends on category, price and competition, and we have no data that would let us put an honest number on it. Treat the result as the cost comparison, then ask whether the conversion difference is worth the gap it shows. Applying a made-up uplift would turn a calculator into a sales pitch.
How is the crossover volume calculated?
FBM carries fixed costs that do not move with order count: a warehouse minimum, a 3PL retainer, shelf space you are already paying for. Those are divided by the number of units you sell. If FBA costs more per unit but FBM carries a fixed monthly bill, there is a volume above which FBM wins and below which it does not. That volume is the fixed monthly cost divided by FBA's per-unit cost advantage. Below it, you are paying for capacity you are not using.
Why do returns cost more under FBM?
Because the return shipping is yours. Under FBA, Amazon handles the return leg for most customer-reason returns and the unit goes back into your inventory; under FBM you pay the carrier to bring it back and you absorb the damage. The calculator charges that shipping only on the share of units that come back, which is why the return rate field changes the FBM result more than the FBA one.
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