The fees that decide your FBA margin
Most sellers price off their landed cost and forget that Amazon takes a stack of fees before the money reaches them. Three fees do most of the damage:
- Referral fee. A percentage of the sale price, taken on every order. Most categories are 15 percent. Consumer electronics is around 8 percent, clothing and jewelry run higher.
- FBA fulfillment fee. A flat per-unit fee for picking, packing and shipping, set by the product's size tier and weight. A small standard unit costs a few dollars; oversize and bulky items cost much more.
- Storage fee. Charged monthly on the space your inventory occupies, and it roughly triples in the Oct to Dec peak. Slow movers quietly bleed margin here, which is why the calculator shows both seasons.
EU sellers also lose VAT off the top of the sale price and may pay import duties on the way in. The calculator strips VAT before working out fees so your margin is on the money you keep.
Size tier sets your fulfillment fee
Amazon files every product into a size tier from its dimensions and weight, and that tier sets the fulfillment fee. Shaving a fraction of an inch or an ounce can drop you into a cheaper tier, so it is worth checking. The common tiers:
| Tier | Rough US limit | Typical FBA fee |
|---|---|---|
| Small standard | ≤ 15 in, ≤ 1 lb | ~$3.50 |
| Large standard | ≤ 18 in, ≤ 20 lb | ~$3.70–$6.70 |
| Large bulky | ≤ 59 in, ≤ 50 lb | ~$9.70+ |
| Extra-large / oversize | beyond bulky | $26+ |
Rates as of 2026 (US Seller Central fee schedule; EU rate card effective 1 Feb 2026). Exact fees vary by weight and price band, and a fuel and logistics surcharge applies from 17 Apr 2026.
Margin and ROI: what good looks like
A profitable FBA product is not just one with a positive number at the bottom. Experienced sellers aim for at least a 25 to 30 percent net margin and a 100 percent or higher ROI on the cash tied up in each unit. That cushion is what lets you run ads, eat returns and survive a fee increase without flipping to a loss.
Break-even ACoS connects FBA to your ads
Once you know your pre-ad profit, you know your break-even ACoS: the most you can spend on Amazon ads per sale before a unit stops making money. It is your pre-ad profit divided by your net revenue. If it comes out at 30 percent, any campaign under 30 percent ACoS is still profitable and anything above it is burning margin. Plan that side with the ACoS calculator.
Frequently asked questions
How does the Amazon FBA calculator work?+
Enter your sale price, the product's dimensions and weight, the category, and your manufacturing and freight costs. The calculator derives the Amazon size tier, applies the 2026 referral fee for your category, a representative FBA fulfillment fee, and seasonal storage, then shows your net profit, net margin, ROI and break-even ACoS per unit for both the Jan to Sep and Oct to Dec storage seasons.
What is a good profit margin and ROI on Amazon FBA?+
Experienced sellers generally look for at least a 25 to 30 percent net margin after all Amazon fees, and a 100 percent or higher ROI on the cash tied up in each unit (manufacturing plus freight). Anything thinner leaves little room to absorb ads, returns or fee increases.
What fees does Amazon charge FBA sellers?+
The three big ones are the referral fee (a percentage of the sale price, usually 15 percent, lower for electronics and higher for clothing and jewelry), the FBA fulfillment fee (a flat fee based on the product's size tier and weight), and monthly storage fees (charged per cubic foot in the US or cubic metre in the EU, and much higher in the Oct to Dec peak). VAT and import duties also apply for EU sellers.
What is break-even ACoS and why does it matter?+
Break-even ACoS is the most you can spend on Amazon ads per sale before a unit stops making money. It equals your pre-ad profit divided by your net revenue. If your break-even ACoS is 30 percent, any campaign running below 30 percent ACoS is still profitable, and anything above it is losing money on that unit.
Are the FBA fees accurate for US and EU?+
The calculator uses Amazon's 2026 published rates (the US Seller Central fee schedule and the EU rate card effective 1 February 2026) as sensible estimates. Exact fulfillment fees depend on the precise weight and price band, and a fuel and logistics surcharge applies from 17 April 2026, so you can override the FBA fee and referral percentage with your exact Seller Central numbers.
The Target ROAS calculator works your whole P&L backwards to the exact return each product needs on Meta or Google. Free, no signup.