Dimensional Weight Calculator

Dimensional weight (also called DIM weight or volumetric weight) is a pricing method couriers use to account for large, lightweight packages that take up disproportionate space in their trucks and aircraft.

Formula (in inches): DIM weight (lbs) = (Length × Width × Height) / DIM divisor

The divisor varies by carrier, and it has a metric twin. The two columns below are the same density written in different units, so pick the one matching the dimensions you typed:

The conversion between the columns is not arbitrary: one cubic inch is 16.387 cm³ and one pound is 0.4536 kg, so an inch divisor multiplied by 36.13 gives the centimetre one. 139 × 36.13 is 5,022, which the carriers round to 5,000.

Billable weight = whichever is greater, actual weight or DIM weight. Parcel carriers round the result up to the next whole pound or kilogram before they bill it, and so does this calculator.

Air freight does not. An air waybill rounds to the next half kilo, so the same box that a courier bills at 15 kg goes on a waybill at 14.5. That is a difference in contract rather than in arithmetic, and it is why a forwarder quote never quite matches a courier quote on identical cartons. If you are shipping a multi-carton consignment on one waybill, the air freight chargeable weight calculator works across the whole shipment and prices it at your quoted rate per kilo.

A box measuring 20 × 15 × 10 inches has a volume of 3,000 cubic inches. DIM weight at 139 = 3,000 / 139 = 21.6 lbs, billed as 22. If the box contains lightweight clothing weighing only 5 lbs, the carrier still bills 22.

This is why ecommerce sellers sweat packaging dimensions. Reducing box size is usually worth more than reducing package weight. Cutting one inch off each dimension of a 20×15×10 box, down to 19×14×9, drops DIM weight from 21.6 to 17.2 lbs, a 20% cut in what you pay for the same goods.

USPS applies DIM pricing only to Priority Mail packages that exceed 1 cubic foot (1,728 cubic inches, or 28,317 cm³). Below that threshold you pay actual weight, and the calculator applies the exemption for you when USPS is selected.