Dimensional Weight for Amazon Sellers: How DIM Weight Is Calculated and When It Beats Actual Weight
Dimensional weight (DIM weight) is length × width × height in inches divided by a carrier’s divisor, and you are billed on whichever is greater: dimensional weight or actual weight. As of 2026-08-10, the divisor is 139 for UPS package shipments, 139 for all FedEx services, and 139 for USPS rectangular parcels over one cubic foot. That single number sets a hard line: any box lighter than 12.43 lb per cubic foot is billed on the air inside it, not on the product. This guide gives the exact rules per carrier with sources, the density math that tells you which side of the line a SKU sits on, and where the same arithmetic reappears inside Amazon’s own fee schedule. ...