What this FBA vs. FBM calculator actually compares
The model assumes the same Amazon US selling price, unit product cost and category referral percentage for both fulfillment methods. FBA subtracts the referral fee, your FBA fulfillment fee and an allocated monthly storage amount. FBM subtracts the referral fee and your own per-order shipping, packing and handling cost. Each channel displays total modeled selling and fulfillment fees, net profit per unit and profit as a percentage of item price.
“Net fee” here means the fees and fulfillment costs included in this model; it does not include product cost. The higher-profit badge shows only the difference in modeled dollars per unit. It is not a forecast of conversion, Buy Box share, Prime demand or total sales. Keep the same price in both channels to isolate the fulfillment cost trade-off; if you would charge different prices, run each scenario separately.
The formulas, with a $39 worked example
Amazon referral fee = item price × entered referral rate. FBA net fee = referral fee + FBA fulfillment fee + allocated storage. FBM net fee = referral fee + self-shipping cost. Net profit = item price − unit product cost − channel net fee. Net margin = net profit ÷ item price × 100. Amounts are rounded to cents before the final comparison; no margin is shown when price is zero.
For a $39 item with $12 unit cost and a 15% referral assumption, the referral fee is $5.85. Enter $4.55 FBA fulfillment and 0.15 cubic feet stored for one January–September month at the modeled $0.78 per cubic foot; storage rounds to $0.12. FBA net fee is $10.52, profit $16.48 and margin about 42.3%. If FBM shipping and packing costs $6.50, FBM net fee is $12.35, profit $14.65 and margin about 37.6%. FBA is ahead by $1.83 per unit in this example, before excluded costs.
Treat the weight shortcut as a starting point, not a fee quote
The Standard size or Bulky / oversize selector and packed item weight drive an illustrative FBA fulfillment shortcut. It deliberately uses broad classes and cannot classify an ASIN by Amazon’s full size-tier rules. For many products Amazon uses the greater of unit weight or dimensional weight, so a light but large package can cost more than the scale weight suggests. Selling price bands, apparel or dangerous-goods status, holiday peak fees and fuel or logistics surcharges can also change the charge.
Amazon’s 2026 US schedule sets a holiday peak period from October 15 through January 14, with applicable surcharges; its Revenue Calculator and fee preview reflect those charges. Use the calculator’s FBA fee field to enter the current estimated fulfillment fee for your exact product and selling period. The “Use weight shortcut” control restores only the rough planning number. Weight and size changes update that shortcut until you type your own fee.
Estimate storage from packaged volume and time
FBA monthly inventory storage is based on the space the packaged inventory occupies, measured in cubic feet, and Amazon’s daily average volume. Weight alone cannot determine it. The tool multiplies packaged volume per unit by average months stored and the selected base US storage rate: $0.78 standard or $0.56 oversize per cubic foot for January–September, and $2.40 standard or $1.40 oversize for October–December. It then assigns that approximate amount to one sold unit.
The estimate is a planning allocation, not a fee preview. Actual storage is billed monthly on inventory on hand and can vary with stock timing, dangerous goods, aged inventory and utilization. If units sit through both seasonal periods, run separate scenarios or use your own blended storage allowance in the FBA fee field, keeping the storage input at zero to avoid counting the same expense twice.
Add the costs that can reverse the winner
FBA can involve shipping inventory into Amazon, inbound placement, prep, labeling, aged inventory, returns processing, removal and other charges. FBM can involve warehouse rent, labor, packaging, seller-paid delivery, returns and customer service. Advertising and product tax treatment affect both methods. These costs are excluded unless you deliberately fold a per-unit amount into product cost or a fulfillment input. Document your allocation so a comparison is repeatable.
Use a recent FBM carrier invoice and packing cost, then compare with the Amazon Revenue Calculator or Fee Preview for the same ASIN, marketplace and period. If the modeled difference is only a few cents, small changes in return rate or storage duration may matter more than the headline badge. The choice may also depend on delivery speed, inventory control and operational capacity.
Where Etsy fits: a different marketplace and MCF model
Etsy sellers can fulfill orders themselves or use outside providers, including Amazon Multi-Channel Fulfillment (MCF) for eligible off-Amazon orders. MCF can use inventory in Amazon’s network, but it has its own fulfillment rate card. An Etsy sale also incurs Etsy’s listing, transaction and payment processing fees, with possible advertising charges. Applying an Amazon marketplace referral rate or FBA fulfillment fee to that Etsy order would misstate its economics.
Use this page only for Amazon marketplace FBA versus Amazon seller fulfillment. For an Etsy-versus-Amazon decision, calculate Etsy order profit separately with Etsy’s current fee rules and the actual MCF or other shipping quote, then compare on equivalent product and tax assumptions. The higher-profit badge on this page is not an Etsy-versus-Amazon verdict.