How the comparison works
Most "FBA calculators" stop at Amazon's own fees and quietly assume your landed cost is just the supplier price. For anyone importing from China that's the number that hides the real margin. Marginely starts from FOB cost, adds sea freight and duty to get your true landed cost per unit, then runs that same unit through both fulfillment paths so the comparison is apples to apples.
FBA per-unit cost
Referral (category) fee on the sale price, plus Amazon's fulfillment fee, plus your inbound shipping into Amazon and monthly storage. When you leave the fulfillment fee at zero, it's estimated from unit weight using current US size-tier rates as a starting point — enter the exact figure from your Amazon listing for precision.
FBM per-unit cost
Referral fee still applies, but instead of Amazon's fulfillment you carry your own shipping label cost and pack/handling time. FBM usually wins on light, low-volume, or high-storage-cost items; FBA usually wins once volume and Prime conversion scale up.
Break-even volume
If one method has a higher per-unit profit, it wins at every volume and there's no crossover. When FBA has lower per-unit profit but you'd otherwise lose Prime-driven sales, the break-even line shows the monthly volume where FBA's scale advantage would need to kick in. Use it as a planning anchor, not a guarantee.
Import duty by common category
Duty is charged on the FOB value, not the sale price. Rates depend on the HTS code; these are common ballparks for goods imported into the US — always confirm your exact HTS classification:
- Many plastics & household goods: roughly 3–6%
- Textiles & apparel: often 10–32% (one of the highest categories)
- Footwear: frequently 10–20%+
- Electronics & many tools: often 0–3%
- Toys & games: frequently 0%
Tariff actions and Section 301 surcharges can change these significantly and often. Treat the field as your blended landed-duty rate and verify against a current customs ruling or your broker.
Why landed cost decides FBA vs FBM
The fulfillment choice rarely flips a losing product into a winner — landed cost does. If freight and duty push your true unit cost above what either method can carry, no fulfillment tweak saves it. Run landed cost first; then let the FBA/FBM split decide how you keep what's left.
What this tool doesn't include
Returns, PPC/advertising spend, long-term storage surcharges, and removal fees aren't modeled here — they affect both methods but not equally. This is a sourcing-stage screen to see whether a product is worth listing at all, and which fulfillment path starts you ahead. Confirm exact Amazon fees on your live listing before committing inventory.