Overview

Amazon's Fulfillment by Amazon (FBA) program charges sellers a per-unit fulfillment fee every time a product is picked, packed, and shipped to a customer. These fees are determined by two key factors: the product's size tier and its shipping weight. Because FBA fees directly impact profit margins, understanding how they are structured is essential for every seller using Amazon's fulfillment network.

Key Points / What Sellers Need to Know

• Flat fee per unit — FBA fulfillment fees are charged as a flat rate for each unit sold, not as a percentage of the sale price. This means the fee is the same regardless of your product's selling price.
• Size tier classification — Amazon classifies every product into a size tier (such as Small Standard-Size, Large Standard-Size, Small Oversize, or Large Oversize) based on its dimensions and weight. The assigned tier determines which fee schedule applies.
• Shipping weight determines cost — Within each size tier, the specific fee is calculated using the product's shipping weight, which is the greater of the actual unit weight or the dimensional weight. Heavier and larger items cost more to fulfill.
• Annual fee adjustments — Amazon reassesses FBA fees on a yearly basis to account for changes in fulfillment, transportation, and delivery costs. Sellers should review updated fee schedules each year, typically announced in late Q4 for the following year.
• Revenue Calculator available — Amazon provides an FBA Revenue Calculator tool in Seller Central that lets sellers input product dimensions and weight to estimate fulfillment fees before committing inventory to FBA.

How FBA Fees Are Calculated

The FBA fulfillment fee calculation follows a straightforward process. First, Amazon measures your product's dimensions (length, width, height) and weight to assign it to the appropriate size tier. Products that fit within standard-size thresholds — generally under 20 pounds and within certain dimensional limits — receive lower fees than oversize items. Next, Amazon determines the shipping weight by comparing the actual unit weight against the dimensional weight (calculated from the product's volume) and using whichever is greater. The applicable fee is then looked up from the fee schedule based on the size tier and shipping weight band. This entire calculation happens automatically, but sellers should verify their product measurements in Seller Central to ensure accurate tier assignment.