Amazon COGS: How to Calculate Cost of Goods Sold for FBA Sellers
Your Amazon dashboard shows a healthy profit. Your bank account tells a different story. Nine times out of ten, the gap lives in COGS — either it’s wrong, incomplete, or you’re not calculating it at all.
What Is COGS for Amazon FBA Sellers?
COGS is the direct cost of the products you sold during a given period. It’s not what you spent on inventory. It’s the cost of the specific units that left your warehouse (or Amazon’s) and shipped to customers.
That distinction matters. You might buy 1,000 units in Q1. If you sell 600, your COGS only reflects those 600. The other 400 sit on your balance sheet as inventory — an asset, not an expense.
The basic formula:
COGS = Beginning Inventory + Purchases − Ending Inventory
Simple enough in theory. Complicated in practice, especially if you’re sourcing from overseas, managing multiple SKUs, or getting hit with freight costs that vary by shipment.
What to Include in Your Amazon COGS Calculation
This is where sellers leave money on the table — or overstate profit without realizing it. COGS isn’t just the product cost on your purchase order.
1. Product Cost (Unit Cost)
The price you pay your supplier per unit. This should be your landed cost per unit, not just the FOB factory price.
2. Freight and Shipping to Amazon
This includes:
– International freight (air or ocean)
– Customs and import duties
– Domestic trucking to the Amazon fulfillment center
– Any prep center fees directly tied to receiving and shipping product
These costs are part of getting inventory ready for sale. They belong in COGS. Most sellers either expense them separately or forget them entirely. Both are wrong.
3. Amazon FBA Fees (Sometimes)
There’s legitimate debate here. FBA fulfillment fees are sometimes categorized as a selling expense rather than COGS. Either approach is defensible — what matters is consistency. Pick a method, document it, and don’t mix treatments across periods.
My preference: treat FBA fees as a selling expense (below gross profit), because it makes gross margin more comparable to non-FBA benchmarks. But if your business is 100% FBA and you’re comparing margins internally, including them in COGS is fine.
4. Prep and Inspection Costs
If you’re paying a third-party prep center to inspect, label, bundle, or repackage product before it ships to Amazon, that cost is part of getting inventory ready. It belongs in COGS.
5. What Does NOT Belong in COGS
– Amazon advertising (PPC)
– Seller fees and referral fees (these are selling expenses)
– Software subscriptions
– Employee salaries (unless directly tied to manufacturing or prep)
– Storage fees at Amazon (this is an operating expense)
How to Calculate Amazon COGS Step by Step
Let’s work through a real example.
You start the quarter with 500 units valued at $12.00 each → Beginning Inventory: $6,000
You purchase 2,000 more units during the quarter:
– Unit cost from supplier: $10.00
– Freight and duties per unit: $1.50
– Prep center fees per unit: $0.50
– Total landed cost per unit: $12.00
– Total purchased: 2,000 × $12.00 = $24,000
At end of quarter you count 700 units remaining → Ending Inventory: $8,400 (700 × $12.00)
COGS = $6,000 + $24,000 − $8,400 = $21,600
You sold 1,800 units with a COGS of $21,600. That’s $12.00 per unit — which checks out.
The Inventory Costing Method Problem
That example assumed all units cost $12.00. Real life isn’t that clean. Your first shipment might cost $10.00/unit and your third shipment $13.50/unit because freight rates moved.
Which units did you “sell”? The cheap ones or the expensive ones?
This is where your inventory costing method comes in. You have two real options: FIFO (First In, First Out) or weighted average cost. Each will give you a different COGS number, a different ending inventory value, and a different taxable income.
This isn’t a minor accounting detail. On 1,800 units with a $3.50/unit cost variance, you’re looking at a $6,300 swing in COGS — and taxable income. The IRS wants consistency. Pick a method and stick with it.
Learn more about FIFO vs. average cost for Amazon inventory →
Why Most Amazon Sellers Get COGS Wrong
They Use Cash Accounting
Sellers who track expenses when they pay them — rather than when goods are sold — will have wildly inaccurate COGS. You pay for a shipment in January. It arrives in March. You sell it in April. Under cash accounting, that shows up as an expense in January regardless of when you actually sold anything.
Accrual accounting matches costs to the period of sale. It’s the only way to get accurate COGS.
They Forget Freight
Amazon dashboard data doesn’t include your freight costs. If you’re building your P&L entirely from Seller Central reports, your COGS is understated. Guaranteed.
They Don’t Do Physical Inventory Counts
COGS flows through your ending inventory number. If your ending inventory is wrong — because of shrinkage, damaged goods, or miscounts — your COGS is wrong. Do a physical count at least quarterly. Reconcile it against what Amazon says you have in FBA.
They Treat Returns Incorrectly
When a customer returns an item, that unit (if resellable) goes back into inventory. If it’s not resellable, it’s a loss that needs to be recognized. Most sellers either ignore this or handle it inconsistently.
COGS and Your Amazon Profit Margins
Once you have accurate COGS, you can calculate gross profit:
Gross Profit = Revenue − COGS
Gross Margin = Gross Profit ÷ Revenue
For a healthy Amazon FBA business, you’re targeting 30–50% gross margins before advertising and operating expenses. If you’re under 30%, you’re fighting a structural cost problem that ad optimization won’t fix. If you’re calculating COGS incorrectly, you might think you’re at 40% when you’re actually at 28%.
How to Track COGS in Your Accounting System
You need proper accounting software — not just a spreadsheet and Seller Central. QuickBooks Online or Xero both handle inventory accounting, but they require setup to work correctly for an Amazon business.
Key things to configure:
– Inventory as an asset account (not an expense account)
– COGS as a separate income statement line
– A method to enter landed costs (freight, duties, prep) when you receive inventory
– Integration or manual import of Amazon sales data
MuseMinded is an accounting firm specializing in Amazon FBA, Shopify, and DTC ecommerce brands. We set this up for clients regularly — and the number of sellers running with a broken COGS setup is not small.
COGS vs. Total Cost of Selling on Amazon
COGS tells you what it cost to make or buy the products you sold. It doesn’t tell you what it cost to actually run your Amazon business.
Your full cost structure on Amazon looks like this:
| Category | Examples |
|---|---|
| COGS | Product cost, freight, duties, prep |
| Selling Expenses | FBA fees, referral fees, returns |
| Marketing | PPC spend, external traffic costs |
| Operating Expenses | Software, team, professional services |
Gross margin (revenue minus COGS) is a measure of product economics. Contribution margin (gross margin minus selling and marketing) is a measure of how profitable each unit sold actually is. Net margin is what’s left after everything.
Most sellers focus on net margin — which is fine — but you can’t fix net margin without understanding where the leaks are. COGS is where it starts.
Frequently Asked Questions
What is COGS for Amazon FBA sellers?
COGS (Cost of Goods Sold) for Amazon FBA sellers is the direct cost of inventory sold during a period. It includes product cost, inbound freight, import duties, and prep fees — any cost incurred to get inventory ready for sale.
Does Amazon COGS include FBA fees?
It can, but most accountants treat FBA fulfillment fees as a selling expense below the gross profit line. Either treatment is acceptable as long as you’re consistent period to period.
How do I calculate landed cost per unit for Amazon?
Add product cost + inbound freight + import duties + inspection/prep fees, then divide by total units received. That’s your landed cost per unit — the number that should flow into your COGS calculation.
What’s the difference between COGS and inventory purchases?
Inventory purchases are what you spent to acquire stock. COGS is the portion of that stock you actually sold. Unsold inventory stays on your balance sheet as an asset until it sells.
Why does my Amazon COGS keep changing?
COGS changes when your purchase costs change (freight, supplier pricing) and when your inventory costing method interacts with those changes. Switching between FIFO and average cost mid-year also causes fluctuations. Consistency in method reduces volatility.
Can I deduct COGS on my taxes?
Yes. COGS reduces your gross income and therefore your taxable income. This is separate from expensing — COGS is matched to revenue in the period you sell, not the period you buy. Accurate COGS directly affects your tax liability. — ## Get Your Amazon Books Actually Right If your COGS is wrong, your margin is wrong, your taxes are probably wrong, and every business decision you’re making is based on bad numbers. Most sellers figure this out after a painful tax season or a failed attempt to sell the business. [MuseMinded works with Amazon FBA sellers →](/amazon-accountant) to build accurate P&Ls, get COGS right from the ground up, and give you financial visibility that Seller Central was never designed to provide. [See how we work with Amazon sellers →](/amazon-seller-accounting)
MuseMinded is an accounting firm specializing in Amazon FBA, Shopify, and DTC ecommerce brands. If your books aren’t telling you the full story — we can fix that.
