How Amazon FBA Profit Is Calculated
Your true FBA profit is what's left after Amazon's cuts, your product cost, and the costs sellers most often forget — advertising and returns. The core formula is simple, but the inputs are where margins quietly disappear:
Referral fee is Amazon's commission (usually 15% of the selling price). The FBA fulfillment fee is a flat charge based on the item's size and weight tier. COGS is your landed unit cost (manufacturing plus inbound freight and duties). The two line items new sellers leave out — and the two that decide whether a product is actually viable — are advertising cost per unit and the return rate.
A Worked Example
Say you sell a $25.00 product that costs you $6.00 landed:
- Referral fee (15%): −$3.75
- FBA fulfillment fee (small standard): −$3.86
- Landed COGS: −$6.00
- PPC ($2.00 ad spend per unit sold): −$2.00
- Returns (3% × ~$11 loss per return): −$0.33
Net profit ≈ $9.06 per unit, a 36% margin and an ROI of ~151% on your $6.00 cost. Drop the price to $20 or let PPC creep to $4 and that healthy product slips toward break-even — which is exactly why modeling every line item before you source matters.
What Counts as a Healthy FBA Margin
| Net Margin | What It Means |
|---|---|
| 30%+ | Strong — room to advertise and absorb fee increases. |
| 20–30% | Healthy and sustainable for most categories. |
| 15–20% | Workable but fragile — little cushion for PPC or returns. |
| Below 15% | Risky — one fee change or price war can push you negative. |
Margin (profit ÷ revenue) and ROI (profit ÷ cost) tell different stories. A product can have a modest 20% margin but a fantastic 150% ROI if your unit cost is low and inventory turns quickly. Track both before committing to an order.
Common Mistakes That Erase FBA Profit
- Ignoring PPC. Many products look profitable organically but lose money once you fund the ads needed to rank.
- Forgetting storage fees. Slow-moving inventory racks up monthly and long-term storage charges that the per-unit math hides.
- Using FOB cost instead of landed cost. Inbound freight, duties, and prep can add 20–40% to your real unit cost.
- Pricing on margin alone. A 40% margin on a $4 item is still only $1.60 — volume and ROI determine whether it's worth your capital.