USPS Changed Its DIM Divisor to 139: What It Costs You
Updated October 14, 2026
On July 12, 2026, USPS lowered its dimensional weight divisor from 166 to 139 for Priority Mail Express, Priority Mail, Ground Advantage and Parcel Select. It also started rounding each dimension up to the next whole inch. That brings USPS in line with UPS and FedEx, which already use 139 for most domestic services.
Who is affected
USPS only applies DIM pricing to parcels larger than one cubic foot (1,728 cubic inches). Small, dense packages are unaffected. Light, bulky items in large boxes are hit hardest.
The math
DIM weight = length × width × height ÷ divisor, rounded up to the next pound. A lower divisor means a higher DIM weight: about 19% higher for the same box.
| Box | 14 × 12 × 11 in, 3 lb actual |
|---|---|
| Cubic inches | 1,848 |
| DIM at 166 | 12 lb |
| DIM at 139 | 14 lb |
How to fight it
- Right-size boxes. Every inch counts, because each dimension is rounded up.
- Keep boxes at or under 1 cubic foot for USPS where you can. A 12 × 12 × 12 box avoids DIM pricing entirely.
- Use poly mailers for soft goods.
- Check every SKU at once with the bulk tool, or a single box with the DIM weight calculator.
Check your own shipments