Field note6 min read
USPS Dimensional Weight Rules for 2026
The July update moved the USPS divisor from 166 to 139 for applicable services and revised measurement rules.
Effective July 12, 2026
USPS changed the DIM factor from 166 to 139 for listed services including Priority Mail Express, Priority Mail, USPS Ground Advantage, and Parcel Select. The published domestic DIM test generally applies above 1,728 cubic inches.
FORMULA
If rounded cubic size > 1,728 in³: DIM lb = cubic inches ÷ 139
Why the change matters
| Volume | Old divisor 166 | New divisor 139 |
|---|---|---|
| 2,800 in³ | 17 lb rounded | 21 lb rounded |
| 4,000 in³ | 25 lb rounded | 29 lb rounded |
Before mailing
- •Check whether the service is covered.
- •Measure the finished parcel accurately.
- •Review the current Domestic Mail Manual.
- •Check nonstandard and length-plus-girth rules separately.