Compare the dimensional weight above with the actual package weight and use the heavier number to determine shipping cost
*Fractions are rounded to the next whole pound.
Dimensional weight (or DIM weight) is the “weight” used to calculate the shipping cost of bulky, lightweight packages. Think about the available space in a truck or plane—if your package is taking up a bit more space than the weight the package captures in rates, you will pay for that space.
The DIM weight is calculated by determining the cubic size of a package, which can be found by multiplying its length x width x height. If the result is greater than 1728 inches (1 cubic foot) divide by each carrier’s divisor shown below. Shippers will be charged the greater of the Dim weight or the actual scale weight.
UPS and Fed Ex divisor: 139, and applies to all packages
USPS divisor: 166, and applies to Priority Mail, Priority Mail Express, and Non-Lightweight Parcel Select
Dim weight is the weight of a package based on its size rather than "actual weight". UPS, FedEx, and USPS calculate a dim weight for their services and charge the greater of actual scale weight or dim weight to price packages, when applicable.
To calculate, you will first determine the package dimensions in inches. For each package dimension, measure at the longest point, rounding each measurement to the nearest whole number (for example, 9.00 to 9.49 will be considered 9, and 9.50 to 9.99 will be considered 10).
Then, multiply the package length by the width by the height. For USPS, divide this number by 1728 (1 cubic foot). If that outcome is larger than 1, the package qualifies for dimensional weight. If a package qualifies for USPS, divide the length times width times height by the 166 divisor. For all FedEx and UPS packages, you divide by 139 for any package dimensions to get the dimensional weight. The result is your new dimensional weight. For those services where dimensional weight is relevant, take the greater of this calculation or the actual, scale based weight to determine the shipping cost.
All the time for UPS and FedEx services. USPS applies dimensional weight to domestic Priority Mail, Priority Mail Express, and Non-Lightweight Parcel select packages that exceed 1 cubic foot. So, a best practice is to always enter package dimensions to make sure you're getting the best rate possible.
FedEx and UPS have maintained their same divisor for dimensional weight since the beginning of 2018. USPS changed the way they apply dimensional weight starting June 23, 2019.
You'll be paying the higher price between dimensional weight and actual weight. In simple terms, if your package is lightweight but large (like a canvas painting or a pillow), you'll be paying more.