Amazon FBA vs FBM: Which Is More Profitable for Your Product?
The FBA-versus-FBM debate is usually argued in generalities — Prime badge, conversion rate, control, headaches. All real, all unmeasurable in a spreadsheet.
The part that is measurable is the cost stack, and it produces a cleaner answer than the debate suggests: the winner flips with the size and weight of the product. Below is the same comparison run on two products from one catalogue. FBA wins the first by a clear margin. FBM wins the second by a similar one.
Every fee and cost figure below is an assumption chosen to be plausible, not a quoted rate. Substitute your own.
The one line that is identical in both columns
Before anything else: the referral fee does not change. Amazon takes its percentage of the sale price on every marketplace sale whether you ship the box or they do. It is the same number on both sides of every comparison in this article, which means it can never be the reason to choose one over the other.
What changes is what sits underneath it. On the FBA side: the fulfilment fee and monthly storage. On the FBM side: postage, packaging, your labour, and the space the stock occupies.
Product one: a small, light, fast mover
The bamboo cutting board — $24.99, standard size tier, 320 units a month.
| Line | FBA | FBM |
|---|---|---|
| Sale price | $24.99 | $24.99 |
| Referral fee (15%) | −$3.75 | −$3.75 |
| Cost of goods | −$4.10 | −$4.10 |
| Inbound shipping | −$0.80 (to Amazon) | −$0.55 (to you) |
| FBA fulfilment fee | −$5.45 | — |
| Amazon storage | −$0.55 | — |
| Pick and pack labour (5 min @ $15/hr) | — | −$1.25 |
| Packaging and consumables | — | −$0.65 |
| Outbound postage | — | −$6.90 |
| Total cost | $14.65 | $17.20 |
| Net profit per unit | $10.34 | $7.79 |
| Margin | 41.4% | 31.2% |
FBA wins by $2.55 a unit — before you count the Prime badge at all.
The reason is entirely postage. Amazon’s $5.45 covers pick, pack and delivery; buying that delivery retail costs $6.90 and you still have to do the picking and packing yourself. At small sizes, Amazon’s negotiated shipping rates are simply better than yours, and that gap is the whole answer.
And it gets worse for FBM once conversion enters. For FBM to match FBA’s monthly profit here it would need to sell 32.7% more units at $7.79 each — while carrying no Prime badge. That is not a close call.
Product two: bulky and heavy
The orthopedic dog bed — $54.99, oversize tier, 95 units a month.
| Line | FBA | FBM |
|---|---|---|
| Sale price | $54.99 | $54.99 |
| Referral fee (15%) | −$8.25 | −$8.25 |
| Cost of goods | −$16.50 | −$16.50 |
| Inbound shipping | −$3.20 | −$3.20 |
| FBA fulfilment fee (oversize) | −$14.20 | — |
| Amazon storage (bulky) | −$2.90 | — |
| Pick and pack labour | — | −$1.25 |
| Packaging and consumables | — | −$1.40 |
| Outbound postage | — | −$11.50 |
| Total cost | $45.05 | $42.10 |
| Net profit per unit | $9.94 | $12.89 |
| Margin | 18.1% | 23.4% |
FBM wins by $2.95 a unit — the same product catalogue, the opposite conclusion.
Two things drove the flip. The oversize fulfilment fee is nearly three times the standard-size one, while your own postage on the same item rose by only $4.60. And storage on a bulky item is charged on cubic feet, so a dog bed occupies expensive shelf space every single month it does not sell — and at 95 units a month against a 45-day lead time, plenty of them sit for a while.
The number that settles it: the conversion break-even
FBM’s problem is never the cost column. It is that FBM listings generally convert worse than Prime-badged FBA listings. Nobody can tell you by how much for your product, and any specific percentage quoted at you is somebody else’s account data.
So do not guess it. Calculate how much conversion you can afford to lose:
Break-even volume = FBA profit per unit ÷ FBM profit per unit
For the dog bed: $9.94 ÷ $12.89 = 0.771
FBM ties FBA at 77.1% of the current volume. In other words, switching this product to FBM can cost you up to 22.9% of unit sales and you are still no worse off. Anything better than that and you are ahead.
Monthly, at the current 95 units:
| Scenario | Units | Profit |
|---|---|---|
| FBA today | 95 | $944 |
| FBM, no volume loss | 95 | $1,225 |
| FBM, 10% volume loss | 86 | $1,109 |
| FBM, 20% volume loss | 76 | $980 |
| FBM, 22.9% volume loss | 73 | $941 — effectively a tie |
| FBM, 30% volume loss | 67 | $864 |
That table turns an argument into a testable question. A 23% cushion is wide enough to be worth trying. Run the cutting board through the same calculation and the cushion is negative — FBM has to gain volume to break even, which it will not.
What the cost columns do not capture
Three things that belong in the decision but not in the spreadsheet:
Your time is in the labour line, but only at cost. 95 dog beds a month is about eight hours of packing. The $1.25 a unit prices that at $15 an hour. If those eight hours are the difference between launching a new product and not, they are worth considerably more than $15.
FBM makes you responsible for delivery performance. Late shipments and tracking defects fall on your account rather than Amazon’s. That is a genuine operational risk on an FBA product you have been treating as hands-off.
Seller Fulfilled Prime exists and lets FBM listings carry the Prime badge if you can meet Amazon’s performance requirements — which are demanding and change. Check the current criteria before you build a plan around it.
Run it per SKU, not per business
The most common mistake here is treating this as a philosophy. It is not; it is a per-product calculation, and a mixed catalogue usually ends up genuinely mixed: FBA for the small, light, fast-turning items where Amazon’s shipping rates beat yours and the Prime badge does the selling, FBM for the bulky, heavy or slow-moving ones where the fulfilment fee and storage are punishing.
Build it as two columns beside each SKU — total cost FBA, total cost FBM, and the difference — and the answer maintains itself as fees change. The trigger to re-check a product: any fee schedule change, any packaging change that might move a size tier, and any product whose days-of-cover is stretching out, because storage cost scales with time on the shelf.
For the fee-by-fee detail behind the FBA column, see how much Amazon FBA costs per unit. Before you commit to either route on a new product, run your break-even price. And for tracking margin across the whole catalogue once products are live, see the Amazon FBA profit calculator spreadsheet guide.
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Frequently Asked Questions
Is FBM always cheaper than FBA?
No — it depends almost entirely on size and weight. For small, light, fast-moving products, Amazon's fulfilment fee is usually lower than what it would cost you to buy postage, packaging and your own time, so FBA wins on pure cost as well as on conversion. For bulky or heavy products the fulfilment fee climbs steeply and storage becomes significant, and self-fulfilling can be genuinely cheaper. In the two worked examples in this article, FBA wins by $2.55 a unit on a cutting board and loses by $2.95 a unit on a dog bed.
Does the referral fee change between FBA and FBM?
No. The referral fee is a percentage of the sale price and Amazon charges it on every sale made through the marketplace regardless of who ships the box. It is the one line that is identical in both columns of the comparison, which is why it never affects the decision. What changes is everything downstream: the FBA fulfilment fee and storage disappear on the FBM side and are replaced by your postage, packaging, labour and the cost of the space the stock occupies.
How much conversion do I lose by switching from FBA to FBM?
There is no reliable published figure, and any specific percentage you see quoted is somebody's own account data rather than a general rule — so do not build a decision on it. Model it as a range instead. Calculate the break-even: divide FBA profit per unit by FBM profit per unit to find the share of your current volume FBM would need to hold in order to tie. If FBA clears $9.94 and FBM clears $12.89, FBM ties at 77% of the volume, meaning it can lose up to 23% of unit sales before you are worse off.
Can I use FBA for some products and FBM for others?
Yes, and for most catalogues with a mix of sizes that is the right answer rather than a compromise. Run the comparison per SKU and let each product land where its own numbers put it. The common pattern is FBA for small, light, fast-turning items where the fulfilment fee is cheap and the Prime badge does the selling, and FBM for the bulky, heavy or slow-moving items where the fee and storage costs are punishing. Many sellers also keep an FBM listing as a backup on their FBA products so a stockout does not take the listing dark.