Volumetric Weight (Dimensional Weight)
Volumetric Weight (or dimensional / DIM weight) is a notional weight calculated from a shipment's volume rather than its actual mass, used mainly in air freight and express parcels to price cargo that is light but bulky. Because aircraft and vehicles run out of space as well as weight, carriers charge on the chargeable weight — the greater of the actual (gross) weight and the volumetric weight.
It is calculated by dividing the shipment's volume by a standard factor — for air cargo, the IATA rule is volume in cm³ ÷ 6,000 (equivalently 1 m³ = 167 kg). A large box of pillows will "weigh" far more volumetrically than on the scale, so it is billed by volume; a small dense box is billed by actual weight. Understanding volumetric weight is essential to quoting air freight and parcels accurately and to packing efficiently, and it is the air-cargo analogue of the sea-freight freight ton (weight or measure).
Ship a big box of something light and the scale lies about what it costs to fly — volumetric weight is how carriers charge for the space it really occupies. Miss it and an air quote is badly under-costed. It is the single most important pricing concept in air freight and express, and it rewards smarter, denser packing.