Are you paying to ship air? Carriers like FedEx and UPS charge by whichever is greater: the actual weight of your package, or its Dimensional (DIM) weight based on box size.
The Dimensional Weight Formula
DIM Weight = (Length × Width × Height) ÷ Carrier Divisor
Carrier Divisors (2026) - **FedEx:** 139 (Domestic and International) - **UPS:** 139 (Daily Rates) or 166 (Retail Rates) - **USPS:** 166 (Priority Mail over 1 cubic foot)
*Note: A higher divisor is better for you. Because USPS uses 166 instead of 139, large lightweight boxes are significantly cheaper to ship via USPS than FedEx.*
How to Reduce DIM Weight Costs
- Cut the Void Space: If your product is 10" tall and you use a 12" box, you are paying a massive DIM weight penalty. Cut boxes down or buy custom sizes.
- Switch to Polymailers: For apparel and soft goods, polymailers eliminate wasted air space.
- Negotiate Your Divisor: High-volume shippers can negotiate a custom divisor with FedEx/UPS (e.g., getting a 166 or 199 divisor instead of the standard 139).
Use our tool to enter your current box size, click "Optimize", and see how much you could save by shaving just 1-2 inches off your packaging.