A few years ago, FedEx and UPS announced that dimensional (DIM) weight—also called volumetric weight—would be the determining factor for calculating shipping rates on all packages smaller than three cubic feet.
Before that time, carriers used only the actual weight of a smaller package to determine pricing.
That meant shippers, such as e-commerce retailers, could pack a small item in a large corrugated box and fill the empty space with lightweight protective dunnage, such as air pillows or kraft paper.
However, as e-commerce has grown exponentially—to a current $130.9 billion, or nearly 10% of all U.S. retail sales, according to the latest U.S. Census Bureau Quarterly report—carriers realized that their pricing needed to better reflect the amount of volumetric space a package required. Hence the advent of DIM weight charges.