How to calculate your true Amazon profit per unit

Your true Amazon profit per unit is your selling price minus every cost that unit carries: the referral fee, the FBA fulfillment fee, storage, inbound shipping and placement, your landed product cost, ad spend per unit, returns and discounts. Most sellers only subtract the first two and their factory price, which is how a product that “makes $10 a unit” ends up barely breaking even. Once you have the real number, you can also work out your break-even ACoS.

What goes into true profit per unit?

Here’s the full formula:

profit per unit = price − referral fee − FBA fulfillment fee − storage per unit − inbound shipping and placement per unit − landed cost − ad cost per unit − returns cost per unit − discounts per unit

Each piece is worth a closer look, because each one is easy to underestimate.

Which Amazon fees does each unit pay?

Referral fee

Amazon takes a percentage of the total sale price for every item sold. For many categories it’s 15%, but it varies by category and sometimes by price band, and there’s a minimum per item. Because it’s a percentage, it falls when you discount, which matters for deals.

FBA fulfillment fee

A per-unit fee for picking, packing and shipping, based on your product’s size tier and shipping weight. It’s usually the biggest fee for low-priced items. If Amazon has the wrong dimensions on file, you’ll pay the wrong fee on every unit.

Storage

Monthly storage is charged per cubic foot and is higher from October to December. Turn it into a per-unit number: total storage fees for the SKU last month divided by units sold last month. Slow sellers carry a lot more storage per unit than fast ones. Aged inventory can also pick up surcharges.

Inbound shipping and placement

What you paid to get units into Amazon, plus any inbound placement fee. Divide each shipment’s total by the units in it. Our Send to Amazon guide explains how placement options change this number.

Don’t hard-code any fee from a blog post, including this one. Amazon changes fees regularly, usually with an annual update and sometimes mid-year. As of September 2026, the most reliable sources are the FBA Revenue Calculator, the fee preview for each SKU in Seller Central, and the fee pages in Seller Central Help.

Which of your own costs do sellers forget?

• Landed cost, not factory price. Factory price plus freight to the US, duties and tariffs, customs brokerage, trucking to your prep center, and prep and labeling. For imported goods this can add a lot on top of the factory price.
• Ad cost per unit. Total ad spend for the product divided by all units sold, not just ad-attributed ones. This is the per-unit version of TACoS.
• Returns. When a customer returns an item, you refund the price and Amazon returns most of the referral fee, but the FBA fee is generally not refunded, and returned units may not be sellable. Some categories also have a returns processing fee. Turn it into an allowance: return rate × what you lose per return.
• Discounts and coupons. Coupons, Prime Exclusive Discounts and deals lower your price and add their own fees. Average their cost across all units sold in the month.
• Losses you don’t recover. Lost or damaged units you never claim. Checking your FBA reimbursements keeps this small.

Worked example: profit per unit on a $30 product

For example, here’s a standard-size product selling at $30. All numbers are round and made up to show the math. Your real fees will differ.

In this example, the “quick math” (price minus referral fee, FBA fee and factory price) gives $15.50. The true number is $8.50, a 28% margin instead of 52%. That gap is the difference between a product you should scale and one you should re-price.

How do you work out break-even ACoS from this?

Break-even ACoS is the ad cost of sale at which an ad-driven sale makes exactly zero profit. Take your profit per unit before ads and divide by price:

break-even ACoS = profit before ads ÷ selling price

In the example, $11.50 ÷ $30 = about 38%. So:

• A campaign running at 25% ACoS is making money on each ad sale.
• A campaign at 45% ACoS is losing money on each ad sale. It may still be worth it for a launch or to rank a keyword, but that should be a deliberate choice with an end date.
• If you want to keep, say, $5 per ad-driven sale, your target ACoS is ($11.50 − $5) ÷ $30, about 22%.

Note that break-even ACoS uses profit before ads, while true profit uses ad cost spread across all units. Both matter. ACoS tells you whether each campaign pays for itself. Ad cost per unit tells you what advertising costs the whole product.

What changes profit per unit the most?

• Price. A $1 price increase is almost pure profit, minus the extra referral fee. Test small increases.
• Size tier. Slimmer or lighter packaging that drops you a tier can cut the FBA fee on every unit.
• Ad efficiency. Cutting wasted spend with negative keywords lowers ad cost per unit without losing sales.
• Inventory turns. Selling through faster cuts storage per unit and avoids aged-inventory surcharges.
• Freight and landed cost. Bigger, less frequent orders can lower freight per unit, but tie up cash and add storage. Find the balance.

How often should you recalculate?

Recalculate monthly for your top products, and whenever something big changes: a new price, a new freight quote, Amazon’s annual fee update, or a jump in ad spend. A simple spreadsheet with one row per SKU is enough. The discipline matters more than the tool.

A few habits keep the numbers honest:

• Use last month’s actuals, not estimates, for storage, ads, returns and discounts. Your settlement reports and the Payments section of Seller Central show what Amazon actually charged.
• Update landed cost with every purchase order. Freight and tariffs can move a lot between orders, and an old number quietly overstates your margin.
• Check Q4 separately. Higher storage rates, deeper discounts and pricier clicks can make October–December margins look very different from the rest of the year.
• Look at variations one by one. A small size and a large size of the same product can have different size tiers, fees and margins.