How U.S. Companies Calculate Volumetric (DIM) Weight Shipping carriers in the USA don’t just look at how heavy a package is — they also consider how much space it takes up. That’s why they use Dimensional Weight. Here’s how it works in practice: Formula DIM Weight = (Length × Width × Height) ÷ DIM Divisor Example Package Length = 20" Width = 16" Height = 12" Calculate Volume 20 × 16 × 12 = 3,840 cubic inches Apply the Divisor 3,840 ÷ 139 = 27.6 lbs Round Up Rounded to 28 lbs Compare With Actual Weight If the package’s actual weight is only 8 lbs, the carrier charges you for 28 lbs, because the package takes up more space than its weight suggests.