FBA vs FBM Calculator
The comparison every fee table tells you to "model yourself" — modeled. Per-unit costs for both routes, plus the part that actually decides it: what the Prime badge does to your monthly volume.
Side by side
| FBA | FBM | |
|---|---|---|
| Fulfillment cost per unit | ||
| Net profit per unit | ||
| Net margin | ||
| ROI on landed cost | ||
| Estimated monthly units | ||
| Estimated monthly profit |
FBM labor is minutes × your rate — your time is a real cost even when nobody invoices you for it. Per-unit storage on both sides should reflect how long a unit actually sits; remember Amazon's rate roughly triples in Q4.
What this comparison actually involves
Most fee tables end with a paragraph telling you to "model both options for your product." Here's what that modeling has to include, and what this page computes:
- Both routes pay the referral fee. FBM isn't fee-free — it swaps Amazon's fulfillment and storage fees for postage, packaging, labor, and your own space.
- Your labor is a cost. Four minutes a package at $20/hour is $1.33 per order. At 200 orders a month that's ~13 hours of packing — count it, or FBM's "savings" are partly you working an unpaid job.
- The Prime badge changes volume, not just cost. Per-unit profit alone can crown the wrong winner: FBM often looks better per unit while FBA earns more per month, because the badge converts more of the same traffic. The breakeven lift in the verdict is the number that settles it for your product.
- Season matters. FBA storage roughly triples in Q4; FBM postage rises with carrier peak surcharges. Re-run the comparison with peak numbers before the holidays.
Frequently asked questions
Is FBA or FBM more profitable?
Product by product. Per unit, FBM often wins on paper — postage plus packaging plus labor can undercut Amazon's fee, especially for large or slow items. Per month, FBA often wins anyway because the Prime badge converts more of the same traffic. This calculator multiplies both sides out so you compare monthly profit, not per-unit illusions.
Do FBM sellers pay Amazon fees too?
Yes — every sale pays the referral fee (15% in most categories, see the fee tables) plus any selling-plan fee. FBM only skips the fulfillment and Amazon-storage fees.
How much does the Prime badge increase sales?
Amazon doesn't publish it, and it genuinely varies — by category, price, and competition. That's why the lift is your input here, and why the verdict reports the breakeven lift: if your realistic estimate clears it, FBA wins for your numbers.
Can I use FBA and FBM at the same time?
Yes — many sellers run FBA for small fast-turners and FBM for large or slow items, or use FBM as backup on the same listing when FBA stock runs out. Decide per product, not per business.