Carrier dimensional weight rules
Carriers bill the greater of actual weight and dimensional weight, which is the box's cubic inches divided by a divisor. Packgent shows a carrier's rule only once it has been read from that carrier's own page.
Rules
| Carrier | Divisor | Applies | Dimensions rounded | Effective |
|---|---|---|---|---|
| USPS | 139 | above 1,728 in³ | up | 2026-07-12 |
| FedEx | 139 | all sizes | to nearest inch | not stated |
| UPS | Pending: not yet confirmed on the carrier's own page | |||
To price a box, use the dimensional weight calculator; to see where the two rules part ways, read USPS vs FedEx dimensional weight.
The divisor is the number of cubic inches a carrier sells per pound. The same box bills at the same dimensional weight under any two carriers that share a divisor, but rounding still splits them: USPS rounds each side up to the next inch, FedEx to the nearest inch, so a box measuring 12.4 in on a side is billed as 13 in by USPS and 12 in by FedEx. USPS also ignores size below one cubic foot. For ways to stay under these thresholds, see right-sizing boxes.