USPS uses divisor 139 and rounds dimensions up
USPS now uses divisor 139 and rounds length, width and height up to whole inches; rectangular parcels use DIM only above 1,728 cubic inches after rounding. The same package may bill at a higher weight; this site’s USPS row models Priority Mail retail weight pricing.
Our read
Bulky items such as hoodies and blankets are hit hardest. A 16 × 12 × 10 in box holding 5 lb now bills at 14 lb. The simplest fix for apparel is a poly mailer instead of a box: soft packs usually stay under 1,728 cubic inches, so dimensional weight never applies.
Key dates
- Published
- New divisor and rounding take effect; Priority Mail Cubic's maximum dimension also rises from 18 to 22 inches
- We checked the official text
Who is affected
- Sellers shipping US domestic parcels with USPS Priority Mail, Priority Mail Express, Ground Advantage or Parcel Select, at retail or commercial prices.
- Anyone boxing bulky goods such as hoodies, jackets, blankets or pillows in cartons over one cubic foot (1,728 cubic inches, about 12 × 12 × 12 in).
- Sellers who ship T-shirts and other thin items in poly mailers under 1,728 cubic inches are largely unaffected: below that line only actual weight counts.
Run the numbers
| Packaging | Rounded size (in) | Volume (cu in) | Billable weight |
|---|---|---|---|
| Carton 16 × 12 × 10 | 16 × 12 × 10 | 1,920, above 1,728 | 1,920 ÷ 139 = 13.8, rounded up to 14 lb |
| Carton measuring 15.2 × 11.5 × 9.4 | 16 × 12 × 10 (each side rounded up first) | 1,920, above 1,728 | Also 14 lb |
| Switch to a 16 × 12 × 9 carton | 16 × 12 × 9 | 1,728, not above | Actual weight, 5 lb |
| Poly mailer 18 × 14 × 4 | 18 × 14 × 4 | 1,008 | Actual weight, 5 lb |
What to do
- Re-run your usual carton sizes under the new rule: round every side up to a whole inch, then check whether the volume exceeds 1,728 cubic inches.
- Move borderline cartons down a size. In the example above, cutting the height from 10 to 9 inches takes 5 lb of goods from billing at 14 lb back to 5 lb.
- Use poly mailers for apparel where you can; when a carton is needed, size it to the packed goods and leave little empty space.
- If a 3PL or fulfillment service ships for you, ask whether its quotes already use divisor 139 and round-up dimensions.
What the official text says
The Postal Service is changing the DIM factor to 139 to determine the dimensional weight in pounds.
Round up (see 604.7.0) each measurement to the nearest whole inch.
If the result exceeds 1,728 cubic inches, divide the result by 139 and round up (see 604.7.0) to the next whole number to determine the dimensional weight in pounds.