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Seller tools · 3 free calculators
Margin, cash payback, and ad ceiling. Get any one wrong and a product that looks profitable on paper quietly drains your account. These three calculators answer each question with your own numbers, before you commit money.
The three tools
Open any card to see exactly what it computes and the problem it solves.
Enter sell price, cost, category, and dimensions. The calculator subtracts Amazon's referral fee and FBA fulfillment fee and shows your real profit and margin per unit — before you commit to inventory.
Enter price, cost, fees and order quantity. Shows how many units you must sell to recover the entire purchase order — plus the capital tied up, time to payback and full sell-through ROI.
Enter sell price, cost, and fees. Returns the exact ACoS percentage at which PPC campaigns stop making money. Spend above that number and every ad click costs you margin.
Margin first. The FBA Profit Calculator tells you what's actually left after Amazon's referral fee and fulfillment fee — most sellers overestimate this until they see the real number.
Cash second. A good margin doesn't mean a safe order. The Inventory Breakeven Calculator shows how much capital is tied up in a purchase order and how many units must sell before that cash comes back.
Ads third. Once the product is listed and selling, the ACoS Breakeven Calculator sets the ceiling — the exact ACoS where every dollar spent on PPC above it is a dollar of margin gone.
Worth knowing
One extra ounce or a fraction of an inch can push a product into the next size tier, raising the fulfillment fee more than the weight itself would suggest. Check the tier boundary, not just the average.
A healthy blended ACoS across your whole account can still mean specific products are burning cash on ads while others subsidize them. Check breakeven ACoS per SKU, not just the dashboard average.
A 40% margin product can still bankrupt a small operation if the order ties up cash for six months. Payback speed determines how often you can reinvest — margin alone doesn't.
Referral fee rates vary by category, and some products legitimately qualify for more than one. A few percentage points on every unit compounds fast once you're ordering in volume.
FAQ
Start with the FBA Profit Calculator to see your real margin after fees. If the margin works, use Inventory Breakeven before ordering stock, and ACoS Breakeven before running ads.
No. Every calculator works with numbers you type in yourself. Nothing connects to your Amazon account and no data leaves your browser.
Yes, completely free, with no signup and no usage limits.
Most rough math skips the FBA fulfillment fee, rounds the referral fee to a flat 15%, and ignores that referral fees apply to shipping too. Each one quietly eats margin on its own; together they often cut an estimated 40% margin closer to 20%.
It usually means the cost or sell price needs to move, not that the product is dead. Try a higher price point, a cheaper supplier quote, or a smaller first order to lower the capital at risk while you validate demand.