What goes into the profit figure
- Referral fee: Amazon’s category commission on the sale, computed from the rates stored here.
- Selling plan: 39.99 USD per month on Professional, spread over your monthly units, or 0.99 USD per item on Individual.
- FBA fulfilment and storage: entered by you, because they depend on size, weight and season. Copy them from Amazon’s own Revenue Calculator.
- Advertising and returns: entered as a percentage of price, so you can model your own ACoS and return rate.
- Product cost, shipping to Amazon and prep: your costs per unit before the sale.
Margin and ROI are different questions
Margin is profit divided by revenue and tells you how much of each sale you keep. ROI is profit divided by the money you put into a unit (product cost, shipping to Amazon and prep) and tells you how hard your money works. A product can have a modest margin and a strong ROI if it is cheap to buy, which is why sellers who reinvest quickly watch ROI.
A worked example
A $30.00 item in “Everything else”, bought for $8.00, with $1.00 shipping to Amazon, $0.50 prep, a $5.00 FBA fee, $0.20 storage, 10% advertising, a 2% returns allowance and 100 units a month on the Professional plan pays $4.50 referral and $0.40 for the plan share. Total fees and selling costs are $13.70, net profit is $6.80 per unit, margin 22.7% and ROI 71.6%. On the Individual plan the plan share becomes $0.99, so net falls to $6.21.
Common ways FBA profit disappears
- Advertising that eats the margin: a launch ACoS of 30% on a 20% margin product loses money on every ad-driven sale.
- Ignoring returns and damaged units, which refund the buyer and often cannot be resold.
- Long storage: slow stock accrues storage cost every month. Enter a realistic per-unit figure.
- Using a Professional plan with a few sales: the monthly fee is spread over few units and can dominate.
Frequently asked questions
Is the FBA fulfilment fee included automatically?
No. Amazon’s fulfilment fees depend on size tier and weight and are not in our tables, so you enter them. Take the number from Amazon’s Revenue Calculator for your exact product.
How is ROI calculated?
ROI is net profit per unit divided by what you invest per unit: product cost plus shipping to Amazon plus prep. A 70% ROI means every dollar invested comes back with 70 cents of profit.
What is the break-even price?
It is the lowest price at which net profit is zero after all the costs you entered. Pricing below it loses money on every unit.
Which selling plan should I pick?
At 39.99 USD a month versus 0.99 USD per item, the Professional plan costs less once you sell about 41 items a month. Enter your monthly units to see the effect on profit.
Does it include sales tax or income tax?
No. It covers Amazon fees and the costs you enter. Income tax and sales tax obligations depend on your situation and are outside this calculator.