How to Calculate Your True Amazon FBA Profit

Ask an Amazon seller for their revenue and you'll get an exact number. Ask for their profit and you'll usually get a pause, then a range.

That's not carelessness. It's that Amazon never shows you the number. Seller Central reports sales. Your bank shows a settlement deposit every two weeks. Neither one is profit, and the gap between them is where most brands quietly lose money — often on their best-selling product, which is exactly the one they keep buying more of.

Here's how to work out what you actually keep.

Your settlement is not your profit

The deposit that lands in your account is sales minus whatever Amazon happened to deduct during that two-week window. That's it. It is a cash-flow event, not a profit figure, and it's misleading in two directions at once.

It's missing costs Amazon has no idea about — what you paid your manufacturer, what it cost to ship into the warehouse. And it contains costs that belong to a different period entirely: a storage fee for inventory that sold in March, a refund for an order from six weeks ago.

So a settlement can look healthy in a month you lost money. If you're steering on that number, you're steering on noise.

Start with one unit

Profit gets tractable when you stop thinking in months and start with a single unit. Everything else is that number, multiplied, minus your overheads.

For one sale, the money leaves in three groups.

1. What Amazon takes

Fee	What it is	Typical range
Referral fee	Amazon's commission on the sale price	8–15% in most categories
FBA fulfilment fee	Pick, pack and ship, priced by size and weight	Flat fee per unit by size tier
Monthly storage	Charged on the cubic feet you occupy	Higher in Q4 (Oct–Dec)

Referral and fulfilment are per-unit and predictable. Storage is not — it's charged on space over time, so it belongs to your slow movers far more than your fast ones. Split it evenly across units and you'll flatter the products that are actually costing you.

Rates change, and Q4 storage in particular is several times the rest of the year. Always price against the current fee schedule rather than what you remember from last year.

2. What you paid, landed

Your cost of goods is not the invoice price from your supplier. Landed cost is the unit price plus freight, duty, inspection, and the cost of getting it into an Amazon fulfilment centre. For a light, cheap product shipped by air, landed cost can be double the unit price.

Two things trip people up here:

• Inbound shipping is part of COGS, not an overhead. If you book it as a monthly expense, every product looks more profitable than it is, and the heavy ones look best of all.
• COGS is not one number forever. You paid one price in January and a different one in June. If you value today's sales at today's cost, your history is wrong. Cost has to be tied to the batch that actually sold.

3. What you paid to be found

Advertising is a cost of the sale. Not a marketing line item you review quarterly — a per-unit cost, the same as the box it ships in.

The useful measure is TACoS: ad spend as a percentage of total sales, not just ad-attributed sales. ACoS tells you how a campaign performed. TACoS tells you what advertising is doing to the business. A product can run a beautiful 18% ACoS and still be unprofitable once you divide the spend across every unit that moved.

The five that quietly wreck the math

The list above is the part most sellers get to. These are the ones that turn a spreadsheet that says +12% into a bank account that says otherwise.

Refunds cost more than the refund. When you refund an order, Amazon returns most of the referral fee — but keeps a refund administration fee. The fulfilment fee is generally gone. The unit may come back unsellable, in which case you've lost the COGS too. A 5% return rate is not a 5% haircut on revenue; it's meaningfully worse.

Projected long-term storage is not a bill. Seller Central will show you a projected long-term storage charge for aged inventory. It's a forecast of what you'd pay if nothing changed. If the stock sells or you remove it, the charge never happens. Sellers who subtract the projection are inventing an expense; sellers who ignore the real one that lands later get a nasty surprise. Only the fee that actually posted is real.

Fees post late. Amazon does not settle everything in the month the sale happened. Account-level fees and adjustments can land weeks after. This is why a month can look profitable on the 1st and worse on the 20th, with no new sales. A recent month is always an estimate. Judge closed months; treat the current one as provisional.

Lost and damaged inventory is a real cost. Units Amazon loses or damages are COGS that left your business. Amazon reimburses some of it, but not automatically and not always at a fair value. Reimbursements are income; the loss is a cost. Track both or you'll count neither.

Coupons and promotions come off the top. A 20% coupon on a product with a 12% net margin doesn't cut margin to a smaller number. It puts it underwater — and the referral fee is charged on the price before the discount in some cases. Run the number before the deal, not after.

A worked example

Illustrative, but the shape is what matters. A £24.99 product:

Line	Amount
Sale price	£24.99
Referral fee (15%)	−£3.75
FBA fulfilment fee	−£3.10
Storage (allocated)	−£0.22
Landed COGS	−£6.40
Advertising (per unit sold)	−£4.10
Net per unit	£7.42
Net margin	29.7%

Now apply reality. A 6% return rate, where half the units come back unsellable, takes roughly £1.00 off that £7.42. A Q4 storage multiple on a slow month takes more. A 15% coupon takes £3.75 straight off the top — more than the entire fulfilment fee — and turns a good product into a mediocre one.

That's the whole point. The unit looked like 29.7%. It's closer to 20% in a normal month, and it can go negative in a bad one, for reasons that never appear on the sales report.

What good looks like

You don't need perfection. You need a number you trust enough to act on.

1. Per product, not per account. Account-level margin hides the loser inside the winner's average. The decisions you actually make — reorder, kill, discount, advertise — are per product.
2. Landed COGS, dated. Tie cost to the batch that sold.
3. Ads allocated to units. Not a monthly lump.
4. Real fees, not projections. Only count what posted.
5. Trust closed months. Treat the live month as a moving estimate, because it is.

Do this in a spreadsheet and it works, for a while. It breaks at the point where you're pulling settlement reports, storage reports, and ad reports across marketplaces and currencies, and reconciling them by hand every month — which is roughly the point where most brands stop doing it and go back to guessing.

That's the problem Seller Sphere exists to solve. Every fee Amazon charges, tied to the product and the batch that generated it, per marketplace, updated daily — so the number you're steering on is the number that's real.