Overview

Amazon has updated its FBA fee calculation to include dimensional weight, meaning the larger of a product’s actual weight or its volume‑derived weight will determine the size tier and associated fees. The change took effect in early 2024 and directly impacts sellers whose items are light but occupy a lot of space. Understanding the new formula and adjusting packaging can prevent unexpected cost spikes.

Key Points

• Weight vs. volume rule — Amazon now compares actual unit weight with calculated dimensional weight and uses the higher figure for fee tier placement.
• Dimensional weight formula — Volume (cm × cm × cm) divided by 5,000 yields a weight in kilograms that feeds into the fee schedule.
• Fee scope — The revised weight metric applies to standard fulfillment fees, fulfillment‑network fees, and customer‑return processing charges.
• Packaging counted — All external packaging, from poly bags to cardboard boxes, is included in the measured dimensions used for the calculation.
• Exempt categories — Envelope‑size items, certain small‑standard SKUs, and designated special‑oversize products continue to rely solely on actual weight.

How Dimensional Weight Works

1. Measure the package — Record the length, width, and height of the fully packaged unit in centimeters. Example: A plush toy packed in a poly bag measures 38 cm × 28 cm × 22 cm.
2. Calculate dimensional weight — Multiply the three dimensions and divide the product by 5,000. Example: (38 × 28 × 22) ÷ 5,000 = 4.69 kg.
3. Compare with actual weight — Retrieve the item’s net weight from the product listing. Example: The plush toy’s net weight is 0.7 kg.
4. Select the greater value — Use the higher of the two numbers (4.69 kg vs. 0.7 kg) as the “chargeable weight.” Example: Amazon will treat the toy as 4.69 kg for fee tier determination.
5. Assign fee tier — Place the product into the size tier that matches the chargeable weight, then apply the corresponding fulfillment fee. : A 4.69 kg charge pushes the toy from the “Standard‑Size” tier into the “Oversize‑Small” tier, raising the per‑unit fee by roughly $2.30.