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.