What is Dimensional (DIM) Weight?
If you've ever shipped a box full of throw pillows or a lightweight poster tube, you might have been shocked by the shipping quote. That shock is caused by Dimensional Weight (DIM Weight).
Delivery trucks and cargo planes run out of space long before they run out of weight capacity. To maximize their revenue, carriers like FedEx, UPS, and DHL charge based on the physical space a package takes up, rather than just what it says on a scale.
How is DIM Weight Calculated?
The math is straightforward but ruthless:
- Multiply the Length × Width × Height (in inches) to get the cubic volume.
- Divide that volume by the carrier's "DIM Divisor" (usually 139 for FedEx and UPS).
- Compare this calculated DIM Weight to your actual scale weight. The carrier will charge you the higher of the two figures. This final number is known as your "Billable Weight."
Why Packaging Optimization is Crucial
Because of DIM weight pricing, using a box that is just 2 inches too big in every direction can literally double your shipping costs for a lightweight item. E-commerce merchants must continually audit their dunnage (bubble wrap, peanuts) and carton sizes to ensure they aren't paying to ship empty air.