Sellers on Amazon face one big operational choice early: do you want Amazon to store, pack, and ship your products, or do you want to handle fulfillment yourself?

That's the split between Fulfillment by Amazon (FBA) and Fulfilled by Merchant (FBM).

You may also see the term Merchant Fulfilled Network (MFN). In practice, FBM and MFN mean the same thing. Amazon's current seller materials use FBM, so that's what this guide uses.

There's no universal right answer. Fast-moving consumer goods that fit neatly in a box often work well with FBA. Oversized items, slow movers, or products that need custom packaging often make more sense with FBM. Some sellers use both models at the same time, splitting their catalog by SKU or using one method as a backup.

Here's how to figure out which model fits your business.

Amazon FBA vs FBM at a Glance

What FBA Means

With Fulfillment by Amazon, you send your inventory to Amazon's fulfillment centers. Amazon stores it, picks and packs orders, ships them out, and handles customer service and returns.

You pay Amazon for storage (monthly fees plus aged-inventory charges if items sit too long) and fulfillment (per-unit fees based on size and weight). In exchange, you get Prime eligibility by default, access to Amazon's logistics network, and Amazon-managed customer service.

FBA is the outsourcing option. You give up operational control to get speed, Prime access, and less day-to-day logistics work.

What FBM Means

With Fulfilled by Merchant, you keep inventory in your own warehouse or with a third-party logistics provider (3PL). When an order comes in, you pack and ship it yourself.

You're responsible for meeting Amazon's handling-time and transit-time standards, confirming shipments, uploading tracking, and managing customer service and returns. Amazon provides tools like Buy Shipping (discounted carrier rates) and Veeqo (free multichannel shipping software) to help, but the operational work stays with you.

FBM is the control option. You manage your own logistics, keep packaging and branding in-house, and model your own cost structure.

Is MFN the Same as FBM?

Yes, in almost every practical context. Merchant Fulfilled Network (MFN) was Amazon's earlier term for seller-fulfilled orders. The current standard term is FBM, but you'll still see MFN in older articles and some Amazon help pages.

If you're reading about MFN, treat it as FBM.

Key Differences Between FBA and FBM

When FBA Makes Sense

Fast-Moving, Small, Light Products

If you sell items that move quickly and fit Amazon's standard size tiers without triggering oversize fees, FBA often wins. The per-unit cost stays manageable, inventory doesn't sit long enough to rack up aged-inventory charges, and Prime eligibility can boost conversion.

Think: phone accessories, consumables, cosmetics, small kitchen tools.

Teams Without In-House Fulfillment Capacity

If you don't have a warehouse, don't want to manage a 3PL relationship, or can't staff pick-and-pack operations, FBA removes that entire workflow. You trade fees for operational simplicity.

Sellers Prioritizing Prime Reach and Operational Simplicity

Prime members convert at higher rates. If you want the Prime badge without running your own two-day shipping operation, FBA gives you automatic eligibility. You also get Amazon's customer service team handling post-sale issues, which frees up internal support resources.

When FBM Makes Sense

Oversized, Heavy, Fragile, or Slow-Moving Inventory

Large or heavy items get expensive fast in FBA. Dimensional weight fees, oversize surcharges, and long-term storage costs pile up. If your product sits in a fulfillment center for months, aged-inventory fees kick in.

Fragile items or products that need special handling can also be risky in a high-volume fulfillment network. FBM gives you tighter control over how items get packed and shipped.

Sellers with Warehouse or 3PL Capabilities

If you already have a functioning warehouse or work with a reliable 3PL, FBM can be the lower-cost option. You're already paying for storage and labor. Routing Amazon orders through that same system avoids double-dipping on fulfillment costs.

Brands That Need More Packaging or Customer Experience Control

Custom packaging, branded inserts, handwritten thank-you notes, and special unboxing experiences all require control over the packing process. FBA uses standard Amazon boxes. FBM lets you design the full customer experience from the package up.

How Costs Really Compare

FBA Fees to Model

When you model FBA costs, include:

Fulfillment fees: Per-unit charges based on size and weight tier
Monthly storage fees: Charged per cubic foot, higher during Q4
Aged inventory surcharges: Kick in at 271 days, increase at 365+ days
Inbound placement fees: If Amazon splits your shipment across multiple fulfillment centers
Returns processing fees: For items customers send back

Amazon's Revenue Calculator lets you compare FBA fees against your own fulfillment costs for specific ASINs.

FBM Cost Buckets to Model

FBM isn't free. You're paying for:

Storage: Warehouse rent or 3PL storage fees
Labor: Pick, pack, and ship time (internal staff or 3PL per-order charges)
Packaging: Boxes, tape, inserts, branded materials
Shipping: Carrier rates (Amazon Buy Shipping offers discounts, but you're still paying per label)
Returns handling: Labor and restocking costs when items come back
Customer service: Time spent answering questions, processing returns, handling issues

The mistake sellers make is comparing FBA's all-in fee against just the shipping label cost for FBM. You have to model the full stack.

Why Margin, Turnover, and Storage Time Matter More Than Headline Fees

A $5 FBA fee looks painful on a $20 item, but if that item moves in two weeks and converts 30% higher because of Prime, the fee can still pencil.

A $3 FBM shipping label looks cheap, but if you're also paying $2 in labor, $1 in packaging, and the item sits in your warehouse for six months eating up storage costs, the total cost can exceed FBA.

Run the math by SKU. Model best-case and worst-case turnover. Factor in the cost of your own time.

For sellers managing inventory across multiple fulfillment paths, common inventory management strategies can help you build a more structured approach to stock planning and turnover.

Should You Use Both FBA and FBM?

Split by SKU Type

Many sellers use FBA for their winners and FBM for the rest. Fast movers go to FBA for Prime eligibility and hands-off logistics. Slow movers, oversize items, or SKUs with thin margins stay FBM to avoid long-term storage fees.

This is a portfolio approach. You're matching method to product, not picking one model for everything.

Backup Offer Strategy When FBA Inventory Runs Low

You can create both an FBA offer and an FBM offer for the same ASIN. If your FBA stock runs out or gets delayed at an inbound checkpoint, your FBM offer keeps the listing active. You lose the Prime badge temporarily, but you don't lose the sale.

This is especially useful during peak season, when FBA inbound delays spike.

When a Hybrid Setup Reduces Risk

If you rely 100% on FBA and Amazon changes fees, loses a shipment, or restricts your inventory limits, you're stuck. If you rely 100% on FBM and your 3PL goes down or you can't keep up with volume, you're also stuck.

Splitting your catalog gives you operational redundancy. You're not betting the whole business on one logistics path.

For brands evaluating their broader fulfillment and distribution options, Amazon's Warehousing and Distribution program is worth understanding as part of the logistics mix.

How to Choose the Right Fulfillment Model for Your Business

FAQ

Next Step for Brands That Need Fulfillment Support

If you're running into margin pressure, storage headaches, or logistics bottlenecks on Amazon, SupplyKick's supply chain team can help you model the right fulfillment mix, build a cost structure that works, and scale without breaking operations.

We work with brands that need more than basic FBA advice. If you're managing a portfolio of SKUs with different margin profiles, turnover rates, and logistics needs, we'll help you build a system that actually works.

Talk to the team.