Amazon FBA guide
Amazon FBA Fee Planning: What to Model Before Buying Inventory
An FBA product can look profitable while the seller is quoting the wrong size tier, forgetting inbound freight or using an optimistic advertising assumption. This guide shows how to build an auditable unit model and why current Seller Central data is more reliable than a fee table copied into an article.
Separate fees into four layers
Referral fees are generally tied to category and selling price. FBA fulfillment fees depend on the product's measured size and shipping weight. Inventory costs include storage and any aged-inventory exposure. Selling costs include PPC, coupons, returns, prep and inbound placement decisions. Keeping these layers separate makes a mismatch easier to diagnose.
Use the current official calculator
Amazon changes fee schedules and adds category or size-specific rules. Amazon's 2026 seller announcement says US referral and FBA fees increased by an average of $0.08 per unit and directs sellers to the current fee pages. For a real SKU, use Amazon's Revenue Calculator or the fee preview in Seller Central, then save the date and product dimensions beside the result.
Worked example: kitchen organizer
| Line | Amount | Evidence to save |
|---|---|---|
| Selling price | $27.99 | Planned offer price |
| Referral fee | −$4.20 | Current category preview |
| FBA fulfillment | −$4.85 | Revenue Calculator result |
| Landed cost | −$7.10 | Supplier invoice plus inbound freight |
| Storage and return allowance | −$1.30 | Conservative per-unit reserve |
| PPC per order | −$5.25 | Target derived from break-even ACoS |
| Contribution profit | $5.29 | Before fixed overhead and tax |
The fee numbers above are illustrative inputs, not a current quote. The useful part is the evidence column. A model becomes trustworthy when another person can see where each number came from and when it was checked.
Dimensions can overturn the product decision
Packaging changes can move a product into another fulfillment tier. Measure the retail-ready packaged unit, not the bare product. Record length, width, height and weight after final packaging. When Amazon measurements differ, investigate the discrepancy before placing a larger order because a small fee change repeated across thousands of units can erase expected profit.
Connect PPC to unit economics
Break-even ACoS equals profit before ads divided by ad-attributed sales. In the example, profit before PPC is $10.54, so the theoretical break-even ACoS is about 37.7%. A seller who wants a 12% contribution margin after ads cannot spend to that ceiling. The target ACoS must be lower, leaving room for the desired profit and data volatility.
Add the cost of being wrong
Contribution profit does not show cash tied up in slow inventory. Before reordering, calculate weeks of cover, supplier lead time and the downside if sales fall. A product with a healthy unit margin but nine months of stock can still be a poor use of cash.
Pre-purchase audit
- Confirm category and referral fee in the current account.
- Run the final packaged dimensions through the official Revenue Calculator.
- Include prep, labeling, inbound freight and placement-related costs.
- Model a return allowance and at least one slower-sales storage scenario.
- Set target ACoS below break-even ACoS.
- Reconcile the first settlement reports with the original model.
Sources and verification
Platform rules can change. These links are provided so readers can verify current terms before acting.
- Amazon announcement: 2026 US referral and FBA fees — official update and link to current fee details
- Amazon FBA Revenue Calculator — current SKU-level estimate; sign-in may be required
Amazon fees depend on size tier, category and storage conditions. Use current Seller Central figures for the exact SKU rather than the planning example.