Updated June 17, 2026
Calculate dimensional weight for your package
Enter your package dimensions and see the DIM weight alongside actual weight.
The formula is: DIM weight = (Length x Width x Height) / DIM divisor. UPS and FedEx use a divisor of 139 for domestic shipments. USPS uses 166, which produces a lower DIM weight for the same box size. Whichever is higher, DIM weight or actual weight, is what the carrier bills. A 14 x 12 x 10 inch box has a volume of 1,680 cubic inches. Divide by 139 and you get 12.1 lbs. If the package actually weighs 4 lbs, the carrier charges for 12.1.
(The divisor is also called the DIM factor. It exists to let carriers recover the cost of truck and aircraft space. A pillow weighing 1 lb but packed in a cubic-foot box takes up the same volume as a 12 lb book. DIM weight is how carriers charge accordingly.)
Why carriers use DIM weight
Transport vehicles fill up by volume long before they reach their weight limits. A truck full of large, light packages runs out of space just as fast as a truck full of heavy ones. DIM weight pricing discourages shippers from over-boxing and ensures carriers recover the real cost of the cubic footage they sell.
Which carriers apply DIM weight
UPS and FedEx apply DIM weight to all packages where DIM weight exceeds actual weight. USPS applies DIM weight only to Priority Mail and Priority Mail Express packages larger than 1 cubic foot (1,728 cubic inches). Packages under that threshold shipped via USPS are billed by actual weight only, which is one reason USPS can be cheaper for certain light, small packages.
How to minimize DIM weight charges
- Use the smallest box that safely fits the item. Every inch of empty space increases DIM weight.
- Use packaging that conforms to the product shape rather than generic square boxes, where possible.
- For items that are already heavy relative to their size, DIM weight rarely applies. Focus right-sizing effort on light products in large boxes.
- Run the DIM weight calculation before choosing packaging, not after.
Worked examples
| Package dimensions | Volume (cu in) | DIM weight (139) | DIM weight (166) |
|---|---|---|---|
| 14 x 12 x 10 in | 1,680 | 12.1 lbs | 10.1 lbs |
| 18 x 14 x 12 in | 3,024 | 21.8 lbs | 18.2 lbs |
| 10 x 8 x 6 in | 480 | 3.5 lbs | 2.9 lbs |
| 24 x 18 x 16 in | 6,912 | 49.7 lbs | 41.6 lbs |
DIM weight rounded to one decimal place. Carriers round up to the next whole pound for billing. Verify current divisors with your carrier before quoting.
Calculate dimensional weight for your package
Enter your package dimensions and see the DIM weight alongside actual weight.