How DIM weight is calculated
DIM weight = length × width × height (in inches) ÷ the carrier’s divisor. Carriers then bill the greater of actual and DIM weight, rounded up to the next pound.
| Carrier | Common divisor | Notes |
|---|---|---|
| UPS | 139 | Divisor can differ by service and account |
| FedEx | 139 | Divisor can differ by service and account |
| USPS | 166 | Only for packages over 1 cubic foot (1,728 in³) |
Example
A 14 × 10 × 8 in box is 1,120 in³. Divided by 139 that is 8.06 lb, billed as 9 lb — even if the product weighs only 4 lb.
How to lower your billable weight
- Use the smallest box that protects the product — each inch off every side cuts volume fast.
- Switch to poly mailers for soft goods like clothing.
- Avoid “one box fits all”: keep two or three box sizes for your main products.
- Ask your carrier about negotiated divisors if you ship high volumes.
Check any box size in the Dimensional Weight Calculator.