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 for every shipment, compare that to its actual weight, and use the greater of the two to determine your shipping cost. Divide the cubic size by 166 if measured in inches, or by 6,000 if measured in centimeters, to determine the dimensional weight. For example: A 19" x 17" x 14" box with an Actual Weight of 5 lbs has a Dimensional Weight of 27 lbs