Dimensional weight, also called "dim" weight, is used because the space a package takes on an aircraft may cost more than the package's actual weight. You should calculate dimensional weight on every shipment, compare that to its actual weight, and use the greater of the two to determine your shipping cost. International and domestic dimensional weights are calculated differently.

For Domestic Shipments:
L x W x H (cubic inches) / 194 = Dimensional Weight.
Example: 30" x 24" x 22" = 15,840 / 194 = 82 lbs. (round up to the nearest pound)