Why size can cost more than scale weight
US parcel carriers may compare actual weight to dimensional weight and charge the higher figure, subject to service rules.
A working formula
DIM weight (lb) ≈ (L × W × H in inches) ÷ divisor. A commonly published UPS/FedEx domestic divisor is 139. Verify before you ship. USPS uses different thresholds.
Source check date: September 8, 2026. Run numbers in the dimensional weight calculator. Smaller cartons start at box size. Format also changes billed profile: mailers vs boxes.