FBA vs FBM: How to Compare the Real Cost per Order
By Raúl Vaquerizo Tortosa · Published October 26, 2026
Choosing between Fulfillment by Amazon (FBA) and fulfilling orders yourself (FBM, “fulfilled by merchant”) is one of the biggest cost decisions an Amazon seller makes. The comparison is often done badly: FBA fees are visible in one place, while the cost of doing it yourself is spread across postage receipts, packaging orders, labour and storage. This guide shows how to put both on the same footing.
Compare only what differs
Some costs are the same whichever way you fulfil:
- The referral fee is charged on the sale either way.
- The product cost and the cost of getting goods into your country do not change.
- Your advertising may differ slightly (more on that below), but it is not a fulfillment cost.
Leave those out of the fulfillment comparison, or include them identically on both sides. What you are really comparing is the cost of storing a unit, getting it to the customer and handling any return.
What FBA costs per unit
| Cost | What it covers |
|---|---|
| FBA fulfillment fee | Picking, packing, delivery and customer service for the order, set by size tier and weight |
| Monthly storage | Space in Amazon’s warehouses, usually per cubic foot and higher in peak season |
| Inbound shipping | Getting stock from your supplier or warehouse into Amazon’s network |
| Prep and labeling | Labels, bagging or bundling, whether you do it or pay for it |
| Other program fees | Depending on marketplace and program, for example inbound placement, low-inventory or aged-inventory fees |
Take the current figures for your marketplace, category and size tier from Seller Central. Fees change, so recheck them at least once a year and whenever Amazon announces changes.
What FBM costs per unit
| Cost | What it covers |
|---|---|
| Postage | The carrier label, based on billable weight and destination |
| Packaging | Boxes, mailers, void fill, tape |
| Labour or pick-and-pack fee | Your own time (or staff), or a 3PL’s handling fee |
| Storage | Your own space, or a 3PL’s storage fee, spread over units |
| Receiving | Unloading and putting stock away, or a 3PL’s receiving fee |
| Returns | Return labels and the time to inspect and restock |
| Software | Shipping or inventory software, divided by orders |
The most commonly forgotten items are your own time and storage space at home or in an office. Both are real costs even if you never write a cheque for them.
An illustrative comparison
The numbers below are invented to show the method. They are not Amazon’s fees or any carrier’s rates.
| Per unit | FBA | FBM via a 3PL | FBM, self-fulfilled |
|---|---|---|---|
| Fulfillment / pick and pack | $5.40 | $3.00 | - |
| Postage | included | $6.20 | $6.20 |
| Packaging | included | $0.50 | $0.50 |
| Labour (4 minutes at $18/hour) | - | - | $1.20 |
| Storage | $0.20 | $0.15 | not counted |
| Inbound shipping / receiving | $0.70 | $0.25 | - |
| Prep and labeling | $0.30 | - | - |
| Total | $6.60 | $10.10 | $7.90 |
In this example FBA is the cheapest per unit, mainly because postage is bundled into the fulfillment fee at a rate a small seller could not match on their own. The self-fulfilled option looks cheaper than the 3PL, but only because storage space is “free” - which stops being true once stock outgrows a spare room.
The ranking changes with the product. Heavy, bulky or slow-moving items often pay high FBA storage and fulfillment fees, and FBM can win for them. Small, light, fast-moving items usually favour FBA.
Costs that are hard to put a number on
Some differences do not fit neatly into a per-unit table:
- Conversion. FBA listings typically carry the Prime badge, which many sellers find helps sales. You can test this with your own listings; do not assume a number.
- Customer service and returns. FBA handles most customer contact for fulfilled orders. With FBM, that time is yours.
- Control. FBM lets you choose packaging, inserts and carriers, and keeps stock where you can use it for other sales channels.
- Cash and risk. FBA requires sending stock to Amazon in advance, and unsold stock incurs storage fees and eventually removal or disposal costs.
How to run the comparison for your products
- Pick one representative product, or one per size tier you sell.
- Get the current FBA fees for it from Seller Central and enter them in the Amazon FBA calculator.
- Price the FBM side: postage from your carrier rates (the shipping cost calculator helps), packaging, labour and storage. If you would use a 3PL, enter its price sheet in the 3PL cost calculator to get a cost per order.
- Compare the per-unit totals, then weigh the unquantified factors above.
- Repeat for your heaviest and slowest-moving products - they are where the answer most often flips.
Many sellers use both
FBA and FBM are not all-or-nothing. A common pattern is FBA for small, fast sellers and FBM for oversized or slow items, or FBM as a backup when FBA stock runs low. Running the numbers per product, rather than for the whole catalogue at once, usually gives a better answer than a single choice.