Amazon FBA Calculator — profit, margin & ROI.

How the Amazon FBA Calculator works

An Amazon FBA calculator turns a selling price into a contribution-margin P&L by stacking every fee Amazon charges against your COGS. The output is what most sellers actually care about: profit per unit, net margin and ROI on landed cost. Get those three right before you launch and the rest of the operation — advertising, inventory planning, pricing — gets honest math to work against.

The fees the calculator models

• Referral fee — Amazon's marketplace commission, a percentage of price (most categories 15%, electronics 8%, apparel 17%). Subject to a $0.30 minimum.
• FBA fulfilment fee — per-unit pick/pack/ship by size tier and weight. The single biggest controllable fee — shaving a box into the next-smaller tier can move margin by dollars.
• Monthly storage — cubic-foot charge that doubles in Q4 and escalates sharply for aged inventory past 181 days.
• Inbound shipping — freight from supplier to FC, plus prep and the Inbound Placement Service Fee, amortised per unit.
• Returns reserve — most categories run 3–8% returns; apparel and shoes much higher. Sellers who ignore this line discover it on the quarterly P&L.
• Ad spend (TACOS) — total advertising cost amortised across all units sold, not just the ad-attributed ones.

Profit, margin and ROI — three different questions

Profit per unit tells you whether the SKU pays its way. Net margin tells you how resilient it is to a price cut or a fee hike. ROI tells you how hard your working capital is working — a 30% margin SKU with $4 landed cost has a far better ROI than a 30% margin SKU with $40 landed cost, even though both look identical on a margin chart.

What healthy unit economics look like on FBA

• Net margin < 10% — fragile. A fee update, a Lightning Deal or a competitor undercut wipes it.
• 10–20% — workable. Most sustainable private-label programmes live here.
• 20%+ — comfortable. Room to discount, advertise more aggressively, and weather Amazon's annual fee changes.
• ROI < 50% — capital-intensive. Cash conversion cycle becomes the bottleneck before scale does.

The line most sellers underestimate

Ad spend. New sellers model FBA fees carefully and then guess TACOS at 5–10%. Launch TACOS for a competitive ASIN is regularly 25–40% for the first 60–90 days; mature-state TACOS for a category-3 keyword strategy is rarely below 12%. Run this calculator with the launch number and the steady-state number side by side — that gap is the cash you need to fund the launch.

What this calculator doesn't do

It is a unit-economics model, not an accounting system. It does not account for VAT/sales tax, FX, long-term storage surcharges past month 12, removal fees, lost-inventory reimbursements, or chargebacks. For a full vendor or seller P&L with those lines wired in — and with real ad-spend pulled from Amazon Ads — that is what AMALYZE is built for.

From calculator to optimization

A calculator answers "can this SKU be profitable?" AMALYZE answers the next question: "which keywords, bids and listing changes get it there?" The calculator above is the honest baseline. AMALYZE is the system that improves it — automated keyword harvesting to lower TACOS, AI listing audits to lift conversion, and bid management that holds the ACoS and margin you just modelled.

More terms in the Amazon seller glossary: COGS, PPC, Amazon FBA, Target ACoS, incremental ACoS.