The FBA calculator says you're profitable. Your settlement report disagrees. Here's why.
You checked your revenue. Numbers looked good. You placed the reorder.
Then the bank deposit came in $800 short.
That gap almost always traces back to one thing: your FBA calculator walkthrough skipped half the fees. Most sellers run a surface-level calculation, see a positive number, and ship. Amazon has other plans.
This post walks through a real product, every fee line, and the actual dollar numbers behind each one - so you know exactly what survives before it lands in your account.
Why Most FBA Profit Calculations Are Wrong
The number one mistake isn't picking a bad product. It's building your profit model on incomplete data.
Amazon's own Revenue Calculator covers two things: referral fees and fulfillment fees. That's it. PPC, inbound shipping, returns processing, storage, prep costs -none of it appears. You're working with maybe 60% of your real cost structure.
A product that looks like it earns $9/unit at the calculator stage can realistically deliver $2–3 after full accounting. That's not a margin - that's a rounding error that disappears the second ACOS creeps up or you get a bad return week.
Full FBA Profit Calculator Walkthrough: Real Numbers on a $27.99 Product
Let's use a kitchen gadget. Selling price: $27.99. Ships standard. Weighs 12 oz packaged.
Line 1 - Referral Fee
Amazon charges 15% on kitchen products.
$27.99 × 15% = $4.20
Line 2 - FBA Fulfillment Fee
Small standard item (10" × 6" × 4", under 1 lb): $3.56 per unit in 2026.
Pull this from Amazon's Revenue Calculator using your packaged dimensions - not your product dimensions. A box that's even slightly oversized bumps you to the next tier and adds $1.00–1.20 per unit, every single order.
Line 3 - Inbound Shipping + Prep
Ocean freight from China + FBA labeling + carton prep: roughly $0.85/unit for a standard-weight item. Freight alone runs $0.40–$0.55/unit; prep adds another $0.20–$0.40 depending on your 3PL or warehouse setup.
Line 4 - FBA Storage Fee
Jan-Sep rate: $0.78/cubic foot/month. This product: 0.08 cubic feet.
At 500 units average inventory: $0.78 × 0.08 = $0.06/unit/month.
Small now. Deadly if that inventory stalls over Q1.
Line 5 - Returns (Blended Cost)
Kitchen category average return rate: ~8%. Amazon charges a $5.00 returns processing fee per unit when it comes back. Most returned units either get resold at a discount or disposed of entirely.
Blended return cost per sale: $0.80/unit.
Line 6 - PPC Ad Spend
At a conservative 25% ACOS: $27.99 × 25% = $7.00/unit in ad spend.
If ACOS climbs to 35% — which happens fast in competitive niches - that number jumps to $9.80/unit.
Line 7 — Cost of Goods (Landed)
Supplier unit price + China-to-US freight + customs duty: $6.50/unit.
The Full Breakdown
18% sounds fine. Push ACoS to 35% and net profit drops to $2.22/unit - a 7.9% margin. One bad return week and you're negative.
What Your FBA Calculator Is Hiding
Dimensional weight traps. Amazon uses the greater of actual weight vs. dimensional weight (L × W × H ÷ 139). A 10 oz product in a slightly bulky box ends up in a higher fee tier. Measure everything packaged.
Long-term storage fees. After 365 days, Amazon charges $6.90/cubic foot/month. 200 unsold units of a slow-mover = $110+ per month in LTSF. Most sellers catch this only after the damage is done. Before reordering, review what fees are actually eating your margin on every ASIN.
2026 fee changes. Amazon updated its FBA fee schedule for 2026 - including inbound placement fees that are now standard, not optional. Old spreadsheet models won't catch this. See the full breakdown of what changed between 2025 and 2026 before running any reorder numbers.
Returns processing fees are real money now. Since 2024, Amazon charges $5.00 per returned unit in most categories. This doesn't get absorbed by Amazon - it comes out of your payout. At a 10% return rate, that's $0.50 per unit sold, every month.
Loss-making ASINs hide in the portfolio. When you have 20+ SKUs, a few bad ones don't scream - they quietly drain margin from the winners. If you haven't audited your catalog for ASINs that are actively losing money, the FBA calculator walkthrough for one product is only half the picture.
Set a Hard Floor Before You List
Here's the rule: if contribution margin is under $4.00/unit after running all 7 cost lines - don't list. Reprice, renegotiate COGS, or pass.
Below $4, a single fee change, an ACoS bump, or a string of returns flips you negative. That's not a business model - that's a bet.
At $6-8 contribution margin, you have real room. You can run a coupon, absorb a slow month, survive a fee update, and still pull profit. You can actually scale.
The sellers who last aren't the ones who found the best product. They're the ones who modeled their numbers honestly before the first shipment.
FAQ
What is an FBA calculator and what does it calculate?
An FBA calculator estimates your profit on an Amazon product by subtracting Amazon's fees from your selling price. It typically covers referral fees and FBA fulfillment fees. A complete FBA calculator should also include PPC spend, inbound shipping, prep costs, storage, and returns - costs that Amazon's built-in tool doesn't show.
How accurate is Amazon's FBA Revenue Calculator?
Amazon's free FBA Revenue Calculator is accurate for referral and fulfillment fees only. It misses PPC costs, return processing fees, long-term storage fees, and inbound prep - which together typically add 10–20% to your total costs. Use it as a starting baseline, then layer in the remaining cost lines manually to get accurate unit economics.
What is a good profit margin for FBA products in 2026?
A healthy FBA net margin after all costs - including PPC - is 15–25%. Target at least $4–6 in contribution margin per unit as a hard floor. Anything below $4/unit net leaves too little buffer for fee changes or return spikes. Most profitable FBA sellers aim for 20%+ before they scale ad spend.
How do FBA fulfillment fees get calculated?
FBA fulfillment fees are based on the product's size tier (small standard, large standard, oversized) and the greater of actual weight or dimensional weight. For 2026, fees start at $3.06 for small standard items under 2 oz and increase by size and weight band. Always measure packaged dimensions - not product dimensions - to land in the correct fee tier.
Why does my FBA payout always come in lower than the calculator showed?
The gap almost always comes from PPC spend, returns processing fees, inbound placement fees, and storage charges that weren't factored into the original number. Amazon's calculator shows a best-case scenario. Your actual settlement report shows reality - every deduction, including the ones that don't have obvious line items.