What dimensional weight is
A big, light box takes up as much room on a truck as a heavy one, so carriers charge for space too. Dimensional weight is length × width × height in inches, divided by a number called the divisor. The carrier bills whichever is greater, the dimensional weight or the actual weight, rounded up to the next pound.
The divisors
UPS and FedEx commonly use 139 for domestic shipments at their standard prices. USPS uses 166, and only for packages larger than one cubic foot (1,728 cubic inches). Business accounts can have different divisors, so check yours.
How to pay less
Use the smallest box that protects the item. Cutting an inch off each side of a 14-inch cube takes about 20% off its dimensional weight. Poly mailers and padded envelopes avoid most dimensional charges for soft goods.
Questions people ask
How do you calculate dimensional weight?
Multiply length × width × height in inches, divide by the carrier's divisor (139 for UPS and FedEx at standard prices, 166 for USPS on boxes over one cubic foot), and round up to the next pound.
Does USPS charge dimensional weight?
Only for packages larger than one cubic foot (1,728 cubic inches). Smaller USPS packages are priced by actual weight.