Net profit per unit and monthly profit after Amazon FBA fees

Why Amazon Margin Math Is Not Obvious

Amazon FBA sellers quote gross margins that rarely match their bank deposits. The gap is fees. Three fee streams hit every FBA sale: referral fee (usually 15% of selling price, varies 6-20% by category), FBA fulfillment fee (flat dollar amount based on weight and dimensions, typically 3-10 for standard-size items), and monthly storage fee (volume-based, higher in Q4 when inventory sits pre-holiday). A product selling for 30 with a 10 product cost looks like 67% gross margin. After 4.50 referral + 4 fulfillment + 0.50 storage, actual net margin is about 37% — still good but nowhere near the gross number.

Referral Fee Percentages by Category

Most categories: 15% of selling price. Amazon Devices: 45% (brand-controlled). Gift Cards: 20%. Jewellery: 20% on first 250, then 5%. Personal Computers: 6%. Consumer Electronics: 8%. Books: 15% plus 1.80 closing fee. Grocery: 8-15%. Baby products below 10: 8%. There are minimum referral fees (0.30 per unit for most categories), meaning very low-priced items lose an outsized share to fees. The calculator takes referral percentage as a direct input so you can match your actual category.

FBA Fulfillment Fee Brackets

Amazon charges FBA fulfillment fees based on item size and weight. Small standard (under 1 lb): roughly 3-4 per unit. Large standard (1-3 lb): 4-5. Oversized: 9-35 depending on exact dimensions and weight. Apparel has slightly different fee tiers. Amazon updates these fees 1-2 times per year — check seller central for current rates before finalising a business model. The calculator takes FBA fee as a dollar input so it adapts to whatever bracket your product falls.

Hidden Costs Not in the Calculator

Amazon takes returns refund handling fee (0.50 per return on most items). Long-term storage fee on inventory over 365 days old. Removal or disposal fees if it helps to pull slow-moving stock. Advertising (Amazon PPC typically runs 10-15% of revenue for a profitable campaign). Amazon seller subscription (39.99/month Professional plan). Inbound shipping to Amazon warehouses (roughly 0.50-2 per unit depending on freight method). Tax on profits. Factor these for a realistic picture of net profit reaching your bank account.

Worked Example

Product: reusable water bottle. Selling price 24.99. Cost of product (landed, including inbound shipping from): 6. Referral fee 15% = 3.75. FBA fulfillment fee (medium standard): 4.75. Monthly storage cost: 300. Units sold per month: 800. Per-unit storage: 300 / 800 = 0.375. Profit per unit: 24.99 - 6 - 3.75 - 4.75 - 0.375 = 10.115. Monthly profit: 8,092. Net margin: 40.5%. Healthy. Now add 2,000/month Amazon PPC, and profit drops to 6,092/month — still reasonable but tighter than the per-unit math suggests.

When FBA Does Not Work

Products under 15 selling price often cannot profitably FBA because the 3-5 minimum fulfillment fee plus referral fee plus minimum storage plus product cost leaves no margin. Oversized items (9-35 fulfillment fees) need high margins to absorb fees. Seasonal products that sit in Q4 storage (2.40/cubic foot vs 0.78 off-peak) get eaten by storage costs. Slow-selling products trigger long-term storage fees. The calculator shows current-month math; add a 10-15% safety margin for these seasonal or timing issues.