How to Use This Calculator
- 1
Enter Product Details
Input your sale price, product cost (COGS), referral fee rate (typically 15%), and product weight in pounds. These apply to both FBA and FBM calculations.
- 2
Set Fulfillment Costs
Enter average months in FBA storage (affects storage fees), plus your FBM shipping and packaging costs per unit. The calculator uses weight-based FBA fulfillment fees and $0.083/lb/month storage rates.
- 3
Compare Results and Insights
The calculator shows which method is recommended, plus FBA and FBM net profit with margin and ROI. The Insights panel highlights the fulfillment cost gap, storage sensitivity, and volume projections. Two breakdown bars visualize how each method splits the sale price. The comparison table shows every metric side by side.
Example Calculation
An Amazon seller compares FBA vs FBM for a $35 product weighing 1 lb with $8 COGS, 15% referral rate, 6 months average storage, and $5 shipping + $1 packaging for FBM.
Sale Price
$35
Product Cost (COGS)
$8
Referral Fee Rate
15%
Product Weight
1 lb
Avg. Months in Storage
6 mo
FBM Shipping Cost
$5
FBM Packaging Cost
$1
Results
FBA Recommended
$18.03
FBA Net Profit
$18.03
FBM Net Profit
$15.75
Insights card shows FBA fulfillment+storage ($3.
Tips
Check the Fulfillment Cost Gap
The Insights panel compares FBA fulfillment+storage vs FBM shipping+packaging directly. For this example, FBA costs $3.72 vs FBM's $6.00 — the $2.28 gap is why FBA wins. If your FBM shipping is under $3.72, FBM would be cheaper.
Use Storage Sensitivity to Plan Inventory
The Insights panel shows how storage duration affects FBA profit. Reducing from 6 to 1 month adds $0.42/unit. For 100 units/month, that's $42/month saved. Fast-selling products benefit most from FBA.
Compare the Breakdown Bars Side by Side
The two breakdown bars show how each method splits your $35 sale price. FBA's green (profit) section is larger because its fulfillment costs are lower than FBM's shipping+packaging for this product.
Test Heavy Products to Find the Crossover
FBA fulfillment fees jump at weight boundaries: $3.22 (1lb), $4.75 (2lb), $5.40 (3lb), $6.10 (5lb). Try increasing weight to find where FBM becomes cheaper for your specific shipping rates.
Comparing Amazon FBA vs FBM Fulfillment Costs
The Amazon FBA vs FBM Cost Comparison Calculator helps sellers determine whether Fulfillment by Amazon or self-fulfillment is more profitable per unit.
Enter your product details and fulfillment costs to see net profit, margin, and ROI for both methods, with a detailed comparison table and visual breakdowns.
The calculator accounts for referral fees, FBA fulfillment fees, storage costs, and your FBM shipping and packaging costs.
The Comparison Formula
Both methods share the referral fee.
The difference lies in fulfillment costs:
FBA Net Profit = Sale Price - Product Cost - Referral Fee - FBA Fulfillment Fee - Storage Fee
FBM Net Profit = Sale Price - Product Cost - Referral Fee - FBM Shipping - FBM Packaging
For a $35 product with $8 COGS at 15% referral:
FBA: $35 - $8 - $5.25 - $3.22 - $0.50 = $18.03
FBM: $35 - $8 - $5.25 - $5.00 - $1.00 = $15.75
FBA wins by $2.28 per unit because FBA fulfillment+storage ($3.72) is cheaper than FBM shipping+packaging ($6.00).
Worked Example: $35 General Product, 1 lb
An Amazon seller lists a 1 lb product at $35 with $8 COGS, a 15% referral rate, and 6 months average storage time.
FBM shipping costs $5 and packaging costs $1.
FBA Calculation:
- Referral Fee: $35 × 15% = $5.25
- FBA Fulfillment Fee: 1 lb = $3.22
- Storage Fee: 1 lb × $0.083 × 6 months = $0.50
- FBA Net Profit: $35 - $8 - $5.25 - $3.22 - $0.50 = $18.03 (51.5% margin)
FBM Calculation:
- Referral Fee: $35 × 15% = $5.25
- FBM Shipping: $5.00
- FBM Packaging: $1.00
- FBM Net Profit: $35 - $8 - $5.25 - $5.00 - $1.00 = $15.75 (45.0% margin)
FBA wins by $2.28/unit — at 100 units/month, that's $228/month more profit.
The Insights panel shows that reducing storage from 6 to 1 month would increase FBA profit by $0.42 to $18.45.
FBA Fulfillment Fee Schedule by Weight
| Weight | FBA Fee | vs $5 FBM Shipping |
|---|---|---|
| 0-1 lb | $3.22 | FBA saves $1.78 |
| 1-2 lbs | $4.75 | FBA saves $0.25 |
| 2-3 lbs | $5.40 | FBM saves $0.40 |
| 3-5 lbs | $6.10 | FBM saves $1.10 |
| 5-10 lbs | $7.92 | FBM saves $2.92 |
| 10+ lbs | $10.50 | FBM saves $5.50 |
The crossover point depends on your FBM shipping rate.
At $5/unit FBM shipping, FBA is cheaper up to about 2 lbs.
If your FBM shipping is $7/unit, FBA wins up to about 5 lbs.
When FBA's Non-Cost Advantages Matter
Beyond per-unit cost, FBA provides Prime eligibility, which can increase conversion rates by 20-30%.
A product that converts at 15% with Prime vs 10% without Prime generates 50% more sales — potentially outweighing a small per-unit cost disadvantage.
FBA also handles customer service and returns, freeing seller time.
For sellers valuing time at $25-50/hour, the labor savings on packing, shipping, and support can be worth $1-3/unit depending on volume.
The comparison table focuses on direct costs, but these operational factors can shift the decision for borderline cases.
When FBM Clearly Wins
FBM becomes the clear winner for heavy products (10+ lbs where FBA fees exceed $10.50), slow-selling inventory (where FBA aged inventory surcharges add $1.50-6.90/unit after 181-365 days), and sellers with negotiated carrier rates below FBA's standard fees.
If your product weighs 10 lbs and you can ship for $6, FBM saves $4.50/unit plus avoids all storage risk.
Frequently Asked Questions
What is the main difference between Amazon FBA and FBM?
With FBA (Fulfillment by Amazon), Amazon stores your inventory, picks, packs, ships orders, and handles customer service. With FBM (Fulfillment by Merchant), the seller manages all storage, shipping, and support. FBA charges fulfillment and storage fees; FBM incurs your own shipping and packaging costs. Both pay Amazon's referral fee.
When is FBA more cost-effective than FBM?
FBA typically wins for small, lightweight, fast-selling products. A 1 lb product with $5 FBM shipping costs only $3.72 in FBA fulfillment+storage (6 months), saving $2.28/unit. FBA also includes Prime eligibility, which can boost conversion rates 20-30%. The calculator shows the exact crossover for your product.
When is FBM more cost-effective than FBA?
FBM wins for heavy, bulky, or slow-selling products where FBA storage fees accumulate. A 10 lb product costs $7.92 in FBA fulfillment alone, plus storage. If you can ship for under $8, FBM is cheaper. FBM also avoids long-term storage fees that apply after 365 days in FBA warehouses.
How are FBA storage fees calculated?
This calculator uses $0.083 per pound per month for standard storage. A 1 lb product stored 6 months costs $0.50 in storage. Amazon's actual rates are $0.87/cubic foot (Jan-Sep) and $2.40/cubic foot (Oct-Dec), plus aged inventory surcharges after 181 and 365 days. The calculator provides a reasonable per-unit estimate.
Does FBA automatically qualify products for Prime?
Yes. All FBA products are automatically eligible for Prime free shipping, which is a significant sales advantage. FBM sellers can apply for Seller Fulfilled Prime (SFP), but it requires maintaining strict delivery performance metrics including 1-2 day delivery for most orders.