Dimensional weight, also known as DIM weight, is a calculation used by shipping carriers to estimate the weight of a package based on its dimensions. Because large, lightweight packages occupy significant space on transport vehicles, carriers bill based on whichever is greater: the actual scale weight or the dimensional weight.
Package Dimensions and Calculation
To determine the dimensional weight, the length, width, and height of a package are multiplied to find the total cubic inches. This volume is then divided by a specific DIM divisor set by the carrier. The resulting figure represents the dimensional weight in pounds.
To determine DIM weight for UPS, FedEx, and DHL, multiply the package length, width, and height in inches, then divide the total by 139. For USPS, divide the cubic inches by 166 only if the total volume exceeds 1,728 cubic inches.
| Carrier | DIM Divisor | Condition |
| UPS, FedEx, DHL | 139 | Standard for all packages. |
| USPS | 166 | Applied only if package volume is > 1,728 cubic inches. |
Determining Billable Weight
The carrier compares the Actual Weight of the package against the calculated DIM Weight. The higher of the two values is used as the billable weight to calculate the final shipping cost. Consequently, increasing the size of a package may increase shipping costs even if the physical weight remains the same.