Dimensional Weight Calculator
Find out whether your package will be billed by actual weight or dimensional (volumetric) weight—whichever is greater. Essential for budgeting shipping costs on large, lightweight packages.
About this calculator
Carriers charge based on whichever is greater: the actual physical weight of a package or its dimensional (DIM) weight. Dimensional weight reflects the space a package occupies in a truck or aircraft, not just how heavy it is. The formula is: DIM Weight = (Length × Width × Height) / Divisor, where dimensions are in inches and the divisor is a carrier-specific constant. FedEx and UPS domestic use a divisor of 139; USPS uses 166 for retail and 139 for commercial rates. The billable weight is then: Billable Weight = max(Actual Weight, DIM Weight). If your package is large but light—like a box of pillows—dimensional weight will almost certainly exceed actual weight and determine your shipping cost.
How to use
Say you have a box that is 20 × 15 × 10 inches and weighs 8 lbs. You're shipping via UPS (divisor = 139). Step 1: Calculate volume = 20 × 15 × 10 = 3,000 cubic inches. Step 2: DIM weight = 3,000 / 139 ≈ 21.58 lbs. Step 3: Billable weight = max(8, 21.58) = 21.58 lbs, rounded up to 22 lbs. Despite the package weighing only 8 lbs physically, you will be charged for 22 lbs. Reducing box size is the most effective way to lower this cost.
Frequently asked questions
What divisor should I use for FedEx, UPS, and USPS dimensional weight calculations?
FedEx and UPS both use a divisor of 139 for domestic U.S. shipments when dimensions are in inches and weight is in pounds. USPS uses 166 for retail Priority Mail and 139 for commercial/cubic rates. International shipments often use a metric divisor of 5,000 (centimeters and kilograms). Always verify the current divisor with your carrier, as these values can change and affect your shipping budget significantly.
How can I reduce dimensional weight charges on large lightweight packages?
The most direct approach is to right-size your packaging—use the smallest box that safely contains your product. Avoid excessive void fill that inflates box dimensions without adding necessary protection. Consider flexible poly mailers for soft goods, which have near-zero dimensional weight impact. Some carriers also offer flat-rate options that ignore dimensional weight entirely, which can be cost-effective for light but bulky shipments.
Why do carriers charge by dimensional weight instead of actual weight for large packages?
Aircraft and truck capacity is limited by volume, not just payload weight. A pallet of foam cushions may weigh very little but occupies the same space as dense, heavy goods. Dimensional weight pricing allows carriers to recover the opportunity cost of that cubic space. This system, introduced widely in the early 2000s, incentivizes shippers to use efficient, right-sized packaging and helps carriers maintain profitability on low-density freight.