How FBA profit is calculated
Profit per unit = selling price − referral fee − fulfilment fee − storage − product cost − inbound shipping − other per-unit costs. The referral fee is your category's percentage of the selling price with a $0.30 floor. The fulfilment fee is the flat per-unit pick, pack and ship charge for your size tier, multiplied by the 3.5% fuel and logistics surcharge Amazon added in April 2026. Margin divides profit by the selling price; ROI divides profit by the cash you put into the unit (product cost plus inbound shipping), which is the number that tells you how fast capital turns.
Getting the fees right
Referral percentages differ by category, and a few categories (such as some apparel and grocery price bands) use tiered rates. Fulfilment fees change with size tier, weight and, since 2024, with the item's price band: items under $10 get the low-price rate, and $10 to $50 and over $50 bands differ for small standard sizes. Amazon raised fulfilment fees on 15 January 2026 by an average of $0.08 per unit. The exact figure for your ASIN is in Seller Central, so copy it in rather than guessing.
What is left out
Monthly plan subscription, inbound placement service fees, low-inventory-level fees, aged-inventory surcharges, removal orders, returns processing in apparel and shoes, and Q4 storage multipliers are not per-unit constants and are excluded. Put an average per-unit allowance for advertising and returns in the "other costs" box to see a conservative margin. Sales tax is collected and remitted by Amazon and does not affect the result.