I spend a lot of my time these days in Amazon FBA product research, and I talk to a lot of sellers while I'm at it. Same story keeps coming up, over and over: the product looks profitable on paper, and then the real number quietly isn't.
Here's a version of the conversation I've now had too many times:
"I priced it at $24.99, my cost is $6. There's no way I'm not making money on this."
Then the fees start talking, and the margin starts melting.
The two things that mess sellers up
1. Amazon's built‑in Revenue Calculator only pulls platform fees.
It grabs the referral fee, the FBA fulfillment fee, and storage. Fine so far.
What it does not grab: your first‑mile inbound shipping, prep cost, import tariff, return/refund losses, long‑term storage, disposal fees, and the inbound placement fee that shows up when Amazon splits your shipment across warehouses.
So every serious seller ends up re‑doing the math in a separate spreadsheet, jumping between tabs, copy‑pasting numbers, and introducing a new arithmetic error every time. That's exactly when a "great" product becomes a dud — not because the product was bad, but because the calculation was.
2. The "Other" line item.
Go look at your settlement report. Sellers regularly find charges labeled only as "Other" — removal fees, disposal fees, international freight duties all bundled into one vague bucket. Some of us have seen four‑figure "Other" deductions with no explanation attached. You can't validate what you can't break out.
There's also a quieter tax on top of all this: dimensional weight. Amazon charges fulfillment by package size, not just weight. I've seen sellers eat "shipping adjustment" fees that cost more than the product they were shipping, because the box was a few inches bigger than they'd entered.
Why I couldn't find a tool that fixed this
I tried a whole stack of third‑party Amazon profit calculators. This is the pattern I hit:
- Some lock the actually‑useful cost fields behind a paywall.
- Some force you to create an account before you can run a single calculation. No, thanks.
- The ones that work are almost always FBA‑only — there's no way to switch to FBM when you're comparing fulfillment routes.
- Almost none of them let you model refund loss and prep cost, which is exactly where margin tends to die.
So I built the thing I couldn't find, as part of the MerchCalc toolset.
MerchCalc Amazon Profit Calculator
It's a browser‑based calculator for Amazon sellers running FBA or FBM. All the math runs locally in your browser — none of your product research numbers ever get uploaded, and there's no account to create.
Here's what it handles:
- FBA / FBM switch — model both fulfillment routes on the same product instead of rebuilding everything.
- First‑mile inbound shipping, prep cost, and import tariff — the landed‑cost pieces Amazon's calculator ignores.
- Refund / return loss — plug in your expected return rate and watch what it actually does to profit, instead of discovering it after three months of orders.
- Net profit, profit margin, ROI, break‑even selling price, and max acceptable ACoS — everything a seller needs to judge a product before committing to inventory, in one screen.
- Revenue breakdown chart — see exactly where every dollar goes, instead of staring at a single "profit" number.
- Built‑in profit‑level assessment — a rating like "Excellent: net margin above 15%" that tells you at a glance whether a product has healthy margins.
- Runs offline, in your browser — no data ever leaves your device, no account, no paywall, 100% free.
You can try it here: https://merchcalc.com/tools/amazon-profit-calc
The math that changed my mind about a "good" product
This is a typical mid‑size category example — plug in your own numbers, but the shape of it is real.
Same product, same price: $24.99, product cost $6.00.
How most people run the numbers (selling price minus product cost, plus only the obvious platform fees):
| Line | Amount |
|---|---|
| Selling price | $24.99 |
| Product cost | −$6.00 |
| Referral fee (~15%) | −$3.75 |
| FBA fulfillment (under‑entered weight) | −$3.90 |
| Net profit | $11.34 |
| Net margin | ~45% |
Feels like a winner. You order inventory.
Reality, once the hidden costs actually land — the same product, with dimensional weight, prep, tariff, returns, and storage accounted for:
| Line | Amount |
|---|---|
| Selling price | $24.99 |
| Product cost | −$6.00 |
| Referral fee | −$3.75 |
| FBA fulfillment (dimensional weight) | −$4.80 |
| Inbound shipping + prep + tariff | −$3.10 |
| Return loss (5% return rate + refund admin fee) | −$1.30 |
| Long‑term storage / disposal | −$0.90 |
| Net profit | $5.14 |
| Net margin | ~20% |
Same product. The quick version says ~45% margin; the full picture says ~20%. Neither number is wrong in isolation — the first one just didn't include everything. If you sized your PPC, pricing, and inventory on the 45% version, the 20% reality is a slow bleed you only notice months later.
That gap is the whole reason the calculator exists.
What's next
This is a side project and I'm still iterating. Scenario simulation is on the roadmap — eventually you'll be able to test what a price change or a COGS shift does to your bottom line, without rebuilding your spreadsheet.
If you're an Amazon seller (or an indie builder poking around), I'd genuinely love feedback — what's missing, what's wrong, what you'd want to see next. Bug reports welcome.
What's the one cost you keep forgetting when you estimate Amazon product profit? I'll start: for me it was always the return rate.
Also, if you run a Shopify store, I built a Shopify profit & break‑even calculator too. You can read about it here: Shopify profit calculator article.
Built as part of MerchCalc — free tools for cross‑border sellers, no login, no paywall.
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