Dimensional weight calculator

Dimensional weight is a billable weight derived from a package's size rather than its mass. Carriers charge the greater of actual weight and dimensional weight, because a lorry runs out of space long before it runs out of payload. A box of pillows and a box of books take the same room on the vehicle, so the pillows get billed as though they were heavier.

Multiply length by width by height, then divide by the divisor your carrier uses. In inches and pounds most carriers use 139. In centimetres and kilograms the standard is 5000. So a 14 by 12 by 12 inch box is 2,016 cubic inches, divided by 139, which is 14.5 pounds, rounded up to 15. USPS additionally rounds each measurement up to a whole inch before multiplying, and only applies dimensional weight to parcels that exceed one cubic foot, so a 12 inch cube is not affected at all.

Yes. On 12 July 2026 USPS moved from 166 to 139 and started rounding every fractional inch up rather than to the nearest inch. It applies to Priority Mail Express, Priority Mail, Ground Advantage and Parcel Select, and only to packages larger than one cubic foot. The practical effect is roughly 19% more billable weight on affected parcels: a 14 by 12 by 12 inch box that used to bill at 13 pounds now bills at 15. Note the threshold is a parcel that *exceeds* one cubic foot, so a 12 inch cube — exactly 1,728 cubic inches — is not affected at all.

A larger divisor gives a smaller billable weight, so 166 is cheaper for the shipper. This is why the same box can cost less over a UPS retail counter, which uses 166, than on a UPS account, which uses 139. It is one of the few cases where not having an account works in your favour.

Not always. USPS only applies it above one cubic foot. The major express carriers apply it to every piece, and they measure each piece separately rather than the shipment as a whole — so splitting one heavy box into two light ones usually costs more, not less.