Pick the carrier rate, enter the box size and its actual weight. The calculator rounds like the carrier does and shows which weight you will be billed for.
Billable weight
Dimensional weight
Actual weight, rounded
Volume per box
How dimensional weight works
Parcel carriers charge for the space a box takes up in the truck or plane, not only for its weight. They convert the volume into a "dimensional weight" and bill whichever is higher, the actual or the dimensional weight:
DIM weight = L · W · H ÷ divisor
Billable weight = the larger of DIM weight and actual weight
UPS, FedEx and USPS round each side up to the next whole inch before multiplying, and the result up to the next whole pound. UPS rounds metric results up to the next half kilogram.
Divisors by carrier (October 2026)
Carrier and rate
Divisor
Units
UPS daily rates
139
in³ per lb
UPS retail rates
166
in³ per lb
FedEx (US and international)
139
in³ per lb
USPS, parcels over 1 ft³ (since July 12, 2026; before: 166)
A box of 18 × 14 × 10 in weighs 12 lb. Its volume is 2,520 in³. With the divisor 139 the DIM weight is 18.1, rounded up to 19 lb. You are billed for 19 lb, not 12. Under the old USPS divisor of 166 the same box came to 16 lb.
Pallets and freight
Dimensional weight applies to parcels. Pallets sent LTL in the US are priced by freight class, air freight by chargeable weight, and road freight in Europe by loading meter.
Questions and answers
How do you calculate dimensional weight?
Multiply length × width × height of the box, rounding each side up to the next whole inch, and divide by the carrier's divisor: 139 for UPS and FedEx daily rates and, since July 12, 2026, for USPS. Round the result up to the next pound. You pay for the dimensional weight or the actual weight, whichever is higher.
Which divisor does each carrier use?
UPS daily rates, FedEx and USPS use 139. UPS retail rates use 166. In metric, UPS, FedEx and DHL Express use 5,000 cm³ per kg. Air cargo under IATA rules uses 6,000 cm³ per kg. Contract rates can have a different divisor.
Does USPS charge dimensional weight on every parcel?
No. USPS applies dimensional weight only to parcels larger than 1 cubic foot (1,728 cubic inches) for Priority Mail, Priority Mail Express, Ground Advantage and Parcel Select. Smaller parcels are priced by actual weight.
How can I lower dimensional weight?
Use the smallest box that protects the item. One inch less on each side of an 18 × 14 × 10 in box cuts the volume by about 20% and the DIM weight from 19 to 15 lb.