What is net profit per unit?
Net profit per unit answers the only question that matters for every SKU in your catalog: how much money do I actually keep when one unit sells? It is the sale price minus every cost layer: cost of goods sold, Amazon’s referral fee, FBA fulfillment fee, storage fees, advertising spend, and variable costs like returns and prep.
Most sellers track gross profit (sale price minus COGS and referral fee) but stop short of the full calculation. Net profit per unit goes further by including every fee Amazon charges, your storage allocation per unit, and your ad spend per unit. The gap between gross and net is where margin surprises hide.
This metric is best calculated at the SKU level, not the account level. An account-wide average masks money-losing SKUs that drag down your overall P&L. A single slow-moving oversized product can eat the profit from ten fast-turning small items.
The formula
Net Profit = Selling Price
− COGS (landed cost)
− Referral Fee (typically 15%)
− FBA Fulfillment Fee
− Storage Allocation Per Unit
− PPC Cost Per Unit
− Returns Cost Per Unit
// Net Margin
Net Margin % = (Net Profit ÷ Selling Price) × 100
Example: $34 Home & Kitchen product
Take a standard Home & Kitchen product: $34 selling price, 1.2 lbs actual weight, 10 × 6 × 4 inches. Dimensional weight is 240 ÷ 139 = 1.73 lbs, which exceeds the actual weight, so Amazon bills at 1.73 lbs. That puts it in the large standard 1.5–2 lb tier.
| Cost line | Amount |
|---|---|
| Selling price | $34.00 |
| COGS (landed to Amazon) | −$8.50 |
| Referral fee (15%) | −$5.10 |
| FBA fulfillment fee (1.5–2 lb tier + 3.5% surcharge) | −$5.30 |
| Storage allocation (0.139 cu ft × $0.78, ~45 days) | −$0.16 |
| PPC per unit (10% ACoS) | −$3.40 |
| Returns cost (3% rate × $5.30 processing) | −$0.16 |
| Net profit per unit | $11.38 |
| Net margin | 33.5% |
Change any single variable and net profit shifts: drop the selling price to $29 and net profit falls to $6.68 (23%). Increase return rate to 8% and another $0.27 disappears per unit. The math compounds fast.
Why net profit per unit matters for FBA sellers
Net profit per unit is the foundation of every inventory decision. Reorder quantities, ad budgets, promotion strategies, and pricing decisions all flow from this number. A product with a 15% referral fee, $5.30 fulfillment fee, and rising storage costs can look profitable at the gross level while quietly losing money after the full fee stack.
It also determines how much room you have for advertising. If net profit before PPC is $15, you can absorb a 30% ACoS and still keep $4.80. If net profit before PPC is $7, a 30% ACoS leaves you at negative margin. Knowing this number before setting PPC bids prevents the common trap of scaling ads into unprofitable territory.
Common mistakes
- Using gross margin instead of net. Gross margin ignores fulfillment fees, storage, and advertising. A SKU showing 60% gross margin can drop below 20% net after the full cost stack. Always calculate through to the bottom line.
- Ignoring return costs. Amazon charges a return processing fee on every customer return. At a 3–5% return rate in categories like apparel or electronics, this adds $0.15–$0.30 per unit sold across the catalog.
- Averaging storage fees across all SKUs. Storage costs vary by product volume and sell-through rate. A slow-moving oversized product can consume 10× the storage cost per unit compared to a fast-turning small item. Calculate storage allocation per SKU, not per account.