How do you calculate dimensional weight?

Multiply length × width × height and divide by the carrier's factor: for US parcels at the Postal Service, cubic inches ÷ 139 gives pounds; for air cargo, cubic centimetres ÷ 6,000 gives kilograms. The carrier bills the higher of that and the actual weight.

What does a DIM factor of 139 mean?

That 139 cubic inches of package space are billed as 1 lb. The US Postal Service adopted 139 for its main parcel products from 12 July 2026, for parcels larger than 1 cubic foot.

What is chargeable weight in air freight?

The higher of the shipment's actual gross weight and its volume weight, where volume weight is cubic centimetres ÷ 6,000. Air cargo rates are applied to the chargeable weight.

Term

Dimensional weight

Dimensional weight, or DIM weight, is a billing weight calculated from a package's size rather than what it weighs. Carriers charge the higher of the actual weight and the dimensional weight, so a large, light box pays for the space it takes. Parcel carriers divide cubic inches by a factor such as 139; air cargo divides cubic centimetres by 6,000.

Also called DIM weight, volumetric weight, chargeable weight, dimensional weight pricingUpdated 12 October 2026

Why carriers use it

A truck, plane or parcel van fills up by space as well as by weight. A carrier paid only by weight loses money on a box of pillows; dimensional weight makes the pillows pay for the space they take. The rule everywhere is the same — the higher of the two weights is the one billed.

The formulas

Where	Formula	Notes
US parcels (USPS, from 12 July 2026)	L × W × H in inches ÷ 139 = lb	For parcels over 1 ft³ (1,728 in³); each side rounded up to the whole inch, the result up to the next pound
Air cargo (IATA)	L × W × H in cm ÷ 6,000 = kg	So 1 m³ counts as about 166.7 kg
US LTL	Density in lb/ft³ sets the freight class	Not a billed weight — see freight class

The US Postal Service moved to a factor of 139 for Priority Mail Express, Priority Mail, Ground Advantage and Parcel Select from 12 July 2026, "for consistency with industry standards". Private parcel carriers publish their own factors in their service guides.

Worked examples

Parcel: 24 × 18 × 12 in = 5,184 in³ ÷ 139 = 37.3 → rounded up, 38 lb billed — not its actual 10 lb

The same goods in a 20 × 16 × 10 in box: 3,200 ÷ 139 = 23.02 → 24 lb billed. A smaller box takes 14 lb off the bill.

Air: 120 × 80 × 100 cm = 960,000 cm³ ÷ 6,000 = 160 kg — chargeable weight 160 kg, not its actual 150 kg

The mistake people make

Measuring loosely. A box measured at 23.2 in is billed at 24 in under the Postal Service's round-up rule, so a carton a fraction over a whole inch pays for the next one on every side. The cheapest fix is usually the packaging: right-sized cartons cut dimensional weight on every shipment, with no rate negotiation at all.

FAQ