Amazon FBA vs FBM comes down to one question: who stores and ships your stock. The two are the same marketplace with a different warehouse.
With Fulfillment by Amazon you ship stock to Amazon and it picks, packs, delivers and handles returns. With Fulfillment by Merchant you keep the stock and do all of that yourself. Amazon still takes its referral fee either way.
The choice isn’t a philosophy. It is arithmetic on one product at a time, plus one question about the Prime badge. This page gives you both.
What each side is actually responsible for
| FBA | FBM | |
|---|---|---|
| Who stores the stock | Amazon, and it charges monthly by volume | You, in your space or a third party’s |
| Who picks and ships | Amazon | You |
| Who handles returns | Amazon, with a returns processing fee on some orders | You |
| Who answers the buyer | Amazon, for fulfillment questions | You, within Amazon’s response window |
| Prime badge | Automatic | Only through Seller Fulfilled Prime |
| Late deliveries count against | Amazon | Your account health |
| Referral fee | Charged on both, 5% to 45% by category, most commonly 15%, with a $0.30 minimum | |
| Cash tied up | Stock sits in Amazon’s network before it sells | Stock sits with you, and you can sell it elsewhere |
The last two rows are the ones sellers underweight. FBM doesn’t just move work to you, it moves risk to you: a carrier delay that Amazon would have absorbed becomes a late shipment on your record.
What FBA charges you
Amazon’s own FBA page lists the cost components, and there are more of them than the two everyone quotes:
- Fulfillment fee, per unit, based on the product’s price, weight and dimensions. Price matters now, not just size, because low-priced items have their own lower rate card.
- Monthly storage, charged on your daily average volume in cubic feet, and higher in the last quarter of the year.
- Aged inventory, charged monthly on anything sitting in a fulfillment center for more than 181 days.
- Returns processing, on orders where Amazon gives the buyer free return shipping.
- Inbound placement, for spreading your stock across fulfillment centers instead of sending it to one.
- Removal or disposal, per item, when you want stock back or gone.
Rate cards change, so the number to trust is the one attached to your ASIN today rather than a table in an article. Amazon’s Revenue Calculator, inside Seller Central, is built for exactly this comparison: it puts Amazon fulfillment and Your fulfillment in two columns on the same product. Our FBA calculator does the same job, and this guide walks through reading the output.
How to run the comparison
Both sides share the referral fee and the $39.99 Professional plan, so neither belongs in the comparison. Cancel them out and compare only what differs.
The referral fee and the plan are the same either way, so only these two columns decide it
FBA cost per unit is the fulfillment fee, plus storage divided across the units you expect to sell that month, plus a share of returns processing at your category’s return rate.
FBM cost per unit is postage, plus packaging, plus your storage, plus the minutes it takes to pick and pack, priced at what your time is worth.
Take a 1 lb item selling at $25. Suppose FBA quotes a fulfillment fee of $5.50 and storage works out at $0.20 a unit. That is $5.70.
Doing it yourself, a regional carrier rate of $6.40 plus $0.55 in packaging is already $6.95 before you’ve touched the box. Ten minutes of picking, packing and printing at $20 an hour adds $3.33. FBM costs $10.28.
Now change one number. Make the item 6 lb and awkward. FBA’s fee climbs with weight and size, your own carrier rate climbs more slowly on a regional lane, and the answer flips. That’s why the honest version of this article gives you the method rather than a verdict.
The costs FBM sellers forget
The pros-and-cons lists all say FBM has “lower fees”. That’s true only of the fees Amazon charges. What replaces them:
- Your time, which is the cost most spreadsheets leave at zero and which scales linearly with orders.
- Carrier rates you negotiated alone, against the rates Amazon negotiated across its whole network.
- Packaging and printing, per order, every order.
- Storage, which doesn’t disappear because it’s your garage. It becomes rent you are not charging yourself.
- Returns, which you now inspect, restock or write off by hand.
- Cover. Nobody ships while you have flu, and Amazon’s clock doesn’t pause.
That last one decides more switches to FBA than cost ever does.
What fulfillment really does to the Buy Box
The usual claim is that Amazon’s algorithm favors its own fulfillment. That’s the right conclusion from the wrong reason, and the reason matters when you are deciding.
Amazon picks the Featured Offer, which most people call the Buy Box, on the whole offer: the price the buyer pays including delivery, how fast it arrives, whether it is in stock, and how reliably the seller has performed. FBA offers do well because they score well on those inputs by default, not because the fulfillment method is scored directly.
Which means a well-run FBM offer is not locked out. An FBM seller who ships fast, tracks everything and rarely cancels competes on the same inputs, and an SFP offer competes on all of them. It also means FBA isn’t a shield: an FBA offer priced above the rest of the listing still loses.
Seller Fulfilled Prime: FBM with the Prime badge
“FBM can’t get Prime” is the most repeated claim about these two, and it’s out of date. Seller Fulfilled Prime puts the Prime badge on products you ship yourself.
It isn’t an opt-in. You prequalify on your late-shipment, valid-tracking and cancellation rates, complete a 30-day trial, and then keep meeting the requirements to stay enrolled. In exchange you get Prime branding, and Amazon handles post-order customer service and authorises returns inside the return window. You provide free standard delivery to domestic Prime customers, and you can cap how many fast orders a day you accept so the promise stays keepable.
Two warnings. Amazon has been tightening the delivery-speed rules through 2026, so read the current performance requirements in Seller Central rather than any article quoting a percentage, including the ones that quote them confidently. And SFP is demanding by design: it exists for sellers whose logistics are already good, not as a route to fix logistics that are not.
When FBA is the right answer
- The item is small, light and sells steadily, which is where Amazon’s per-unit rate beats anything you can buy.
- You are competing for the Buy Box against FBA sellers on the same listing.
- Order volume is past the point where packing is a use of your day.
- You want to sell while asleep, on holiday, or ill.
When FBM is the right answer
- The item is heavy, bulky or low-value, where FBA’s fee eats the margin.
- It sells slowly, so storage and the 181-day aged inventory charge would bite.
- It is fragile, perishable, made to order, or needs packing Amazon will not do.
- You already ship for your own site and the marginal order costs you almost nothing.
- You are testing a product and don’t want stock stranded in a fulfillment center.
Switching a listing from one to the other
You change fulfillment on the offer, not on the product, and the ASIN, reviews and ranking history all stay where they are. Going FBM to FBA means creating a shipment and sending units in, and the offer stays merchant-fulfilled until they are received and checked in, which takes days rather than hours. Going FBA to FBM means either selling the remaining units down or paying to have them removed or disposed of.
Two things to plan for. Do not let the offer go out of stock during the handover, because a gap costs you ranking that takes longer to earn back than the switch saves. And decide before you move heavy stock into FBA, not after: getting units out again is a per-item charge on top of the inbound cost you already paid.
Multi-Channel Fulfillment, the third option
There is a middle position that neither label covers. With Multi-Channel Fulfillment, Amazon ships your orders from other channels, your own site or another marketplace, out of the same FBA stock, for a separate fee.
It matters to this decision because it removes the strongest argument for FBM. If you were staying merchant-fulfilled so one pool of stock could serve every channel, MCF gets you that without running the warehouse. Price it before you assume FBM is the only way to sell in more than one place.
You don’t have to choose once
Fulfillment is a per-SKU decision, not an account-wide one
So the useful question is not “am I an FBA seller or an FBM seller”. It is “which of my SKUs is on the wrong one right now”. Run the comparison per ASIN, redo it when your fees or carrier rates change, and treat the answer as temporary.
Whichever way a SKU is fulfilled, SellerSonar tells you when its listing changes, its Buy Box is taken or its keyword rankings move. Start your free 14-day trial.
