Dimensional Weight (DIM Weight)

Dimensional weight (DIM weight) is the inch-and-pound way of expressing volumetric weight, the notional weight a carrier gives a shipment based on the space it takes up. It is the term US airlines, forwarders and parcel carriers use. The carrier compares the DIM weight with the actual weight and bills on whichever is higher; in air freight, that higher figure is the chargeable weight.

The DIM weight formula

1. Measure length, width and height in inches at the outermost points, including the pallet and any bulge or overhang
2. Multiply them to get cubic inches
3. Divide by the DIM factor (also called the DIM divisor) to get pounds
4. Round any fraction up to the next whole pound

Example: a carton of 24 × 20 × 18 in is 8,640 cubic inches. At the air freight factor of 166 that is 52.05 lb, rounded up to 53 lb; if the carton actually weighs 30 lb, it is billed at 53 lb. At UPS and FedEx daily rates the factor is 139, which gives 62.16 lb, rounded up to 63 lb.

Common DIM factors

• 166 for air freight: the inch-and-pound equivalent of IATA's 1:6000 rule. 6,000 cubic centimeters per kilogram works out to about 166 cubic inches per pound
• 139 for UPS and FedEx: the factor both carriers apply at their daily rates (UPS retail rates use 166); contract rates can use a different one

A lower factor gives a higher DIM weight, so 139 bills bulky packages more heavily than 166. The carrier's tariff or service guide decides which factor applies, so check it on every quote.

DIM weight vs volumetric weight

They are the same calculation. Volumetric weight is usually stated in metric, cubic centimeters ÷ 6,000 = kilograms; DIM weight in imperial, cubic inches ÷ 166 = pounds. For air freight the two give essentially the same answer apart from rounding: weights in kilograms are rounded up to the next half kilogram, and weights in pounds up to the next whole pound.

How to keep it down

• Use the smallest carton that protects the goods and cut the void fill
• Ship items knocked down rather than assembled
• Avoid oversized pallets; overhang counts at its outer edge
• Measure accurately at booking, because carriers re-measure and re-bill

The chargeable weight calculator accepts dimensions in inches and weights in pounds and works out the volumetric and chargeable weight from a carton list. See air freight for how the rest of an air quote is built.