Overview

Amazon classifies every product fulfilled through FBA into a specific size tier based on its packaged weight and dimensions. These size tiers directly determine what you pay for fulfillment, storage, removal, disposal, and inbound placement services. Understanding how your products are classified — and how close they sit to tier boundaries — is one of the most practical ways to manage your FBA cost structure.

Key Points / What Sellers Need to Know

• Size tiers are based on packaged dimensions — Amazon measures the unit weight, individual dimensions (longest side, median side, shortest side), and dimensional weight of the item in its shipping-ready packaging, not the product alone.
• Dimensional weight matters — For larger items, Amazon calculates a dimensional weight (length × width × height divided by a dimensional factor) and compares it to the actual unit weight. The greater of the two is used for fee calculations.
• Multiple fee types reference size tiers — FBA fulfillment fees, monthly inventory storage fees, aged inventory surcharges, removal and disposal fees, low-inventory-level fees, and inbound placement service fees all vary by size tier.
• Small differences can mean big cost jumps — A product that barely exceeds a size tier threshold will be bumped into the next tier, potentially increasing per-unit fulfillment costs significantly.
• Amazon periodically updates thresholds — Size tier definitions and the fees attached to them are revised regularly, often during Amazon's annual fee update cycle at the start of each year.

How Product Size Tiers Work

Amazon assigns each FBA product to one of several size tier categories. The classification is determined by evaluating four measurements of the packaged item: unit weight, longest side, median side, and shortest side. For products where the physical dimensions suggest a lighter parcel than the actual weight (or vice versa), Amazon also calculates a dimensional weight and uses whichever value is greater. The primary size tiers include Small Standard-Size, Large Standard-Size, Large Bulky, and Extra-Large, with specific sub-tiers within those groupings. Each tier has precise upper bounds for weight and dimensions, and a product must fall within all of a tier's limits to qualify for that classification.