What an FBA unit really costs you
An FBA sale is charged twice: once as a percentage of what the buyer pays, and once as a flat handling fee that has nothing to do with the price. Those two behave in opposite ways, and confusing them is why listings look profitable in a spreadsheet and lose money in Seller Central.
The percentage charge is the referral fee. It scales with price, so a discount cuts it and a price rise increases it. The flat charge is the FBA fulfilment fee, set by your product's size tier and shipping weight. It is identical on a $12 sale and a $40 sale, so it eats 43% of a cheap unit and 13% of an expensive one. That asymmetry is why low-priced FBA products are so hard to make work.
Around those two sit four costs Amazon does not show you: landed unit cost, inbound freight and duty, storage for as long as the unit waits to sell, and advertising. Advertising is the one left out most often, and on a competitive listing it is frequently larger than the referral fee.
The formula, fee by fee
Start with the sale price and subtract every charge that touches the unit.
Referral fee. Your category rate times the sale price, subject to a per-item minimum. Most categories are 15%; consumer electronics and personal computers sit at 8%; clothing and jewellery are tiered by price. It is charged on the total the buyer pays for the item, which is why raising your price by $1 puts only 85 cents in your pocket at 15%.
Fulfilment fee. A flat amount set by the size tier — small standard, large standard, or one of the oversize bands — and the greater of unit weight and dimensional weight. It covers pick, pack, ship and customer service, and it cannot be inferred from the price. You must look it up.
Storage. Cubic feet per unit times the monthly rate for its tier, times the months it sits there. Four turns a year is three months per unit, not one. Rates rise sharply in the fourth quarter, and aged inventory attracts long-term surcharges.
Landed cost. Supplier invoice plus freight, duty, prep and labelling, divided by the units in the shipment; the landed cost calculator builds it from an invoice and a freight quote.
Advertising. Total PPC spend divided by total units sold. Dividing by ad-attributed units flatters the figure badly; the ACoS calculator converts between the two conventions.
Worked example: a $29.99 private-label unit
You sell a home-goods item at $29.99. Your supplier charges $6.50 a unit, freight and duty add $1.40, the item is large standard size with a $5.20 fulfilment fee, it occupies enough space to cost $0.12 a month in storage, you turn inventory eight times a year, PPC runs $3.00 per unit sold, and you allow 2% for refunds.
- Referral fee. 15% × $29.99 = $4.4985. That is above the $0.30 minimum, so the percentage stands.
- Storage. Eight turns a year means 12 ÷ 8 = 1.5 months. $0.12 × 1.5 = $0.18.
- Total Amazon fees. $4.4985 + $5.20 + $0.18 = $9.8785, or 32.9% of the sale price.
- Landed cost. $6.50 + $1.40 = $7.90.
- Returns allowance. 2% × $29.99 = $0.5998.
- All costs. $9.8785 + $7.90 + $3.00 + $0.5998 = $21.3783.
- Net profit. $29.99 − $21.3783 = $8.61 per unit.
- Net margin. $8.6117 ÷ $29.99 = 28.7%.
- Return on inventory. $8.6117 ÷ $7.90 = 109%.
Now the break-even price. The fixed-per-unit costs are $5.20 + $0.18 + $7.90 + $3.00 = $16.28, and each dollar of price keeps 1 − 0.15 − 0.02 = $0.83. So break-even is $16.28 ÷ 0.83 = $19.61. You have $10.38 of pricing room — which is exactly the number to have in your head before a competitor starts a price war.
How to read net margin and ROI
Read the two together, because they answer different questions. Net margin tells you how fragile the listing is: it is the buffer between you and a fee change. Return on inventory investment tells you how hard your cash is working, which is what limits how fast a self-funded brand can grow.
The rules of thumb private-label sellers use are a net margin of 15–25% after PPC and an ROI on landed cost of at least 50%. Those are not standards — they are the levels at which the cash cycle works. A unit bought overseas takes weeks to manufacture, weeks on the water, then sits in a fulfilment centre, so the same dollar of landed cost is only redeployed a handful of times a year. What you earn on it annually is the ROI per turn multiplied by the number of turns: the worked example above returns 109% of landed cost every time the unit turns, while a listing returning 25% of landed cost has to turn more than four times to match one turn of that.
Two red flags matter more than the headline. If Amazon's share of the sale price is above about 45%, the size tier is usually the culprit, and a smaller retail box or a lighter mailer can move you down a band. If advertising is more than a third of your gross profit, the listing is renting its rank rather than earning it.
Compare across products with gross margin and, if you sell the same SKU elsewhere, against the same unit on eBay or your own store, where the payment processing fee replaces the referral fee.
Amazon US referral fee rates by category
| Category | Referral fee | Notes |
|---|---|---|
| Most categories | 15% | Home, Kitchen, Toys, Pet, Beauty, Sports, Office, Garden, Baby |
| Consumer Electronics | 8% | Also Personal Computers, Camera & Photo, Cell Phone Devices |
| Base Equipment Power Tools | 12% | Corded and cordless power tool base units |
| Grocery & Gourmet Food | 8% / 15% | 8% at $15.00 or less per unit, 15% above |
| Clothing & Accessories | 5% / 10% / 17% | Tiered by item price: under $15, $15–$20, over $20 |
| Furniture | 15% / 10% | 15% on the first $200, 10% on the portion above |
| Jewelry | 20% / 5% | 20% on the first $250, 5% above |
| Watches | 16% / 3% | 16% on the first $1,500, 3% above |
| Media | 15% + closing fee | Books, DVD, Music, Software, Video Games carry a flat per-item closing fee |
| Amazon Device Accessories | 45% | Accessories for Kindle, Fire and Echo devices |
| All categories | $0.30 minimum | Per-item floor on the referral fee, whatever the percentage works out to |
Enter your category's rate above; tiered categories need the blended rate at your price point.
The fulfilment fee is the one number you must look up
Everything else in this calculation you already know from your own records. The fulfilment fee you do not: it depends on the size tier Amazon assigns after measuring and weighing your unit, and on the greater of actual and dimensional weight. Amazon also revises the Selling on Amazon fee schedule periodically and adds placement, low-inventory and aged-inventory charges on top of it.
Pull the current fee for your ASIN from the Revenue Calculator or the fee preview report in Seller Central. If your measured dimensions sit within a few millimetres of a tier boundary, price both tiers here — one tier step can be worth more than your entire net margin.
Mistakes that make an FBA estimate too optimistic
- Dividing ad spend by ad-attributed units. Using that denominator can halve your apparent PPC cost. Divide total spend by total units sold.
- Charging one month of storage. A unit that turns four times a year sits for three months, and fourth-quarter rates are several times the off-peak rate.
- Forgetting the referral fee covers the full amount the buyer pays. Gift wrap and any shipping you charge are inside the fee base.
- Ignoring returns. You refund the price, Amazon keeps a refund administration charge, and the fulfilment fee is gone — a returned unit costs more than the profit it briefly made.
- Using the FOB price as the landed cost. Freight, duty, drayage and prep are routinely a large fraction of the invoice on light, bulky goods.
- Leaving out coupons and deals. Every promotional discount lowers the fee base but lowers your revenue faster.
- Testing only the current price. Check break-even too. If it is within 20% of your list price, one competitor can erase the product.
What this calculator does not model
It is a per-unit contribution model, so it excludes anything that does not vary with one more sale: your Professional selling plan, brand registry work, photography, software subscriptions, and your own time. Divide those by monthly units and subtract if you want a fully absorbed figure.
It also does not model Amazon's per-shipment and inventory-health charges — inbound placement fees, low-inventory-level fees, aged-inventory surcharges, removal and disposal fees — or the capacity limits that can force you to hold stock in a third-party warehouse. Add them into inbound freight or storage as a per-unit estimate.
Finally, it assumes every unit you buy sells at the price you entered. Build in a shrinkage and markdown allowance if you are appraising a whole purchase order, and pair it with the inventory turnover ratio so the storage months you enter reflect reality.
When FBA is the wrong comparison
The FBA fulfilment fee looks expensive next to a postage label, and for slow-moving, heavy or high-value items it often is. Fulfilled by Merchant replaces the fulfilment fee with your real pick, pack and postage cost, keeps the referral fee, and costs you the Prime badge along with the conversion rate that comes with it. Run both cases here — put your true shipping cost in the fulfilment fee field for FBM — and compare profit at a realistically lower conversion rate.
The wider comparison is channel mix. Amazon's take is large but arrives with demand attached. On your own store you swap the referral fee for a payment processing fee and a customer acquisition cost you now pay yourself; on Etsy you pay a smaller percentage and reach a much smaller audience. The question is never which channel charges least, but which delivers a profitable unit at the volume you need — which is why the break-even point calculator belongs next to this one.
Key terms
- Referral fee
- Amazon's commission on a sale, charged as a percentage of the total amount the buyer pays for the item, subject to a per-item minimum.
- Size tier
- The band Amazon assigns from your product's measured dimensions and weight. It sets both the fulfilment fee and the storage rate.
- Dimensional weight
- A billable weight derived from package volume. Amazon charges on the greater of actual and dimensional weight, which penalises bulky, light goods.
- Landed cost
- The all-in cost of getting one unit into a fulfilment centre: supplier invoice, freight, duty, prep and labelling.
- Return on inventory investment
- Net profit per unit divided by landed unit cost. Measures how hard the cash in your purchase order works.