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Introduction
Amazon FBA looks like a straightforward fulfillment solution until the fee invoices arrive. Sellers who calculate profit as selling price minus product cost routinely discover that FBA fees, referral fees, storage fees, and advertising together consume 40% to 55% of revenue -- leaving a margin far thinner than anticipated. According to Jungle Scout's State of the Amazon Seller Report, the average Amazon seller achieves a profit margin of 15% to 26%, but 27% of sellers don't know their own margin. Amazon's fee structure is layered and weight/dimension-based -- a 0.5 lb difference in product weight or a 0.1-inch change in the longest dimension can move a product into a higher fulfillment fee tier. This calculator applies Amazon's 2026 FBA fee structure, referral fee rates by category, and storage fee rates to compute your true net profit per unit sold, so you can source, price, and advertise with accurate numbers.
What This Calculator Does
This Amazon FBA fee calculator takes your selling price, product cost (landed), product dimensions and weight, category (for referral fee rate), monthly sales velocity, and optional advertising cost to calculate: FBA fulfillment fee, referral fee, monthly storage fee allocation per unit, total Amazon fees, and net profit per unit and per month. It includes 2026 FBA fee schedules for standard-size and oversize items.
The Formula
FBA fulfillment fees are tiered by size tier (small standard, large standard, small oversize, medium oversize, etc.) and determined by the greater of actual weight and dimensional weight (length × width × height / 139 for domestic). Referral fees are a percentage of total sales price including shipping (varies by category: 8% for electronics, 15% for most categories, 6% for personal computers). Storage fees are charged monthly per cubic foot of warehouse space occupied. Monthly storage fee per unit = (unit volume in cubic feet) × monthly rate.
Step-by-Step Example
Classify the product's size tier
Product: a kitchen gadget. Dimensions: 8 × 5 × 3 inches. Weight: 12 oz (0.75 lb). Dimensional weight: 8 × 5 × 3 / 139 = 0.86 lb. Billable weight: higher of actual (0.75) and dimensional (0.86) = 0.86 lb. Size: longest side 8 inches, all within 18 × 14 × 8 small standard. Size tier: Small Standard.
Apply FBA fulfillment fee
2026 FBA fulfillment fee for small standard, 0.75-1 lb: $3.56 per unit. (Verify current rates at Seller Central -- fees are updated annually.)
Calculate referral fee
Selling price: $24.99. Kitchen category referral rate: 15%. Referral fee: $24.99 × 15% = $3.75.
Calculate storage and total fees
Unit volume: 8 × 5 × 3 / 1,728 = 0.069 cubic feet. Monthly storage fee rate (non-peak, Jan-Sep): $0.78/cubic foot. Monthly storage per unit sold = depends on inventory turns. At 60 days average storage: $0.78 × 0.069 × (60/30) = $0.108/unit. Total Amazon fees: $3.56 + $3.75 + $0.11 = $7.42. Product cost: $7.20. Advertising (PPC): $2.00. Net profit: $24.99 - $7.20 - $7.42 - $2.00 = $8.37. Margin: 33.5%. ROI: $8.37 / $7.20 = 116%.
Real-World Use Cases
Product Sourcing Viability Assessment
A seller evaluates a Alibaba sample at $4.80 landed cost for a product expected to sell at $19.99. Running the FBA calculator: fulfillment fee $3.22 (small standard under 4 oz), referral fee $3.00 (15%), storage $0.06, PPC estimate $3.50. Net profit: $19.99 - $4.80 - $3.22 - $3.00 - $0.06 - $3.50 = $5.41. Margin 27%. The product passes the minimum 20% threshold. The seller proceeds to sampling.
Evaluating a Price Increase to Offset Fee Changes
Amazon announces a $0.25 fulfillment fee increase effective February 1. A seller with 500 units/month sold at $34.99 with $6.20 current net profit will see profit drop to $5.95 -- a 4% decline. The calculator shows that raising the price to $35.49 (+$0.50) covers the fee increase and adds $0.25 to margin at an expected elasticity of -0.4 (modest volume reduction of 2%): 490 units × $6.45 net = $3,160.50 vs. the current $3,100. A small price increase is the better move.
Deciding Between FBA and FBM (Fulfillment by Merchant)
A seller with high-volume slow-moving inventory considers FBM to avoid storage fees. FBA monthly storage cost on 800 units at 0.12 cubic feet: 800 × 0.12 × $2.40 (peak season rate) = $230.40/month. FBM shipping cost (self-fulfilling): $4.20 per order average vs. FBA $3.56 fulfillment fee -- FBM is $0.64 more per order. At 400 orders/month, FBM shipping premium: $256. The FBA storage savings ($230) do not offset the FBM shipping premium ($256). FBA remains better for this product.
Comparison
| FBA Size Tier | Max Dimensions | Max Weight | Approx. 2026 Fulfillment Fee |
|---|---|---|---|
| Small Standard | 15 × 12 × 0.75 in | 12 oz | $3.06 - $3.56 |
| Large Standard (under 1 lb) | 18 × 14 × 8 in | Under 1 lb | $3.68 - $4.12 |
| Large Standard (1-2 lb) | 18 × 14 × 8 in | 1-2 lb | $4.90 - $5.40 |
| Large Standard (2-3 lb) | 18 × 14 × 8 in | 2-3 lb | $5.70 - $6.10 |
| Small Oversize | 60 × 30 in (longest) | Up to 70 lb | $9.50 - $11.50 |
| Medium Oversize | 108 in (longest) | Up to 150 lb | $12.00 - $18.00 |
Common Mistakes to Avoid
Using actual weight instead of dimensional (billable) weight. Amazon charges the greater of actual weight and dimensional weight. Dimensional weight = (length × width × height) / 139. Products with light but bulky packaging may be billed at dimensional weight even if the actual product weighs little. Always calculate both and use the higher value for fee estimation.
Ignoring long-term storage fees on slow-moving inventory. Amazon charges an additional long-term storage fee for units stored more than 365 days: $6.90 per cubic foot or $0.15 per unit, whichever is greater. For slow-moving products, long-term storage fees can exceed the product cost if inventory sits too long. Model storage duration as part of every FBA sourcing decision.
Using the referral fee rate for the wrong category. Referral fee rates vary from 6% (personal computers) to 20% or more (Amazon Device Accessories). Applying the 15% generic rate to an electronics product that qualifies for 8% overstates costs. Always verify the referral fee rate for your specific product category in Seller Central.
Frequently Asked Questions
Accuracy and Disclaimer
Amazon FBA fee calculations in this calculator reflect the most recently published Amazon fee schedules and are subject to change. Amazon updates fees periodically without notice. Always verify current fee rates in Amazon Seller Central or using Amazon's official FBA revenue calculator before making sourcing or pricing decisions. Results are estimates for planning purposes only.
Conclusion
Every significant FBA sourcing decision should run through this calculator before any inventory commitment. A product that looks viable at the expected selling price may be unprofitable when FBA fees are applied at the correct tier. As Amazon adjusts fees annually (Q1 updates are standard), revisit your calculations at the start of each year. For businesses scaling their Amazon operations with advertising, use the Cost Per Acquisition Calculator to track and optimize advertising cost per unit sold. For the full e-commerce profitability picture beyond Amazon, the Shopify Profit Calculator provides the equivalent analysis for your direct-to-consumer channel.
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