The dimensional weight is the number you get what you take a package’s dimensions and multiply (length * width * height) and divide that number by 139.
This formula is a way for FedEx and UPS to calculate what they consider a ‘reasonable’ weight for the size box. This is important for the carriers since they bill based on the weight of the shipment. For most shipments, the dimensional weight is used when it is greater than the actual weight. The DIM divisor of 139 can de negotiated.