Herminox is six free Amazon calculators for sellers and buyers. Everything runs in your browser — no signup, no email gate, inputs never leave your device. Sellers get FBA profit (2026 fees + fuel), ACoS/TACoS breakeven with max CPC, and inventory recovery: units to get PO cash back after fees. Buyers get unit price, cost per use, and a return tracker with holiday windows and locked capital. Coaches can embed widgets. Independent — not affiliated with Amazon. Confirm fees with Seller Central.
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Maker
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Hey Product Hunt 👋 I’m the maker of Herminox.
I got tired of watching people commit to inventory, ads, or “deals” before running the math — and then discovering the margin was fiction or the return window already closed.
So I built six free calculators that run entirely in the browser:
• FBA Profit — referral + fulfillment + 2026 fuel surcharge
• ACoS / TACoS breakeven + max CPC
• Inventory — units to recover PO cash (sell − fees, not profit)
• Unit price · Cost per use · Return / locked-capital tracker