Understanding USPS Dimensional (DIM) Weight Charges

Most carriers determine shipping costs based on package weight and the distance the package is traveling. In general, the heavier the package, the more it costs to ship. However, if you ship bigger, lightweight items, the shipping rate will be calculated based on the Dimensional Weight, or DIM, instead of the actual weight of the package.

For example, if you ship a basketball, which is a regular size package (not oversized) and is light enough that the carrier could carry the package in one hand, the shipping rate will be based on DIM. Why? Because the basketball will take up more space on the truck than a flat package would, and fewer packages on the truck means less money for the carrier. Basing the shipping rate on the package dimensions more accurately reflects what it costs the carrier to ship a large package that takes up more space.

How to Calculate DIM

If a package exceeds 1 cubic foot (12” L x 12” W x 12” H), the USPS will use the volume of the package, rather than the weight, to determine the cost of shipping.

First, determine the length, width and height in inches, rounding to the nearest whole inch. Multiply length x width x height to determine the cubic size. Divide the cubic size by 194 (or 166 for international destinations). Round the resulting DIM up to the nearest full pound. For example, if the DIM equals 10.39, round up to 11 pounds.


For Example: What Happens When A 2-lb Box Exceeds 1 Cubic Foot (12 x 12 x 12) & DIM Is Applied?

Priority Mail 12” x 12” x 14” 2 lbs LA to Chicago $9.62
DIM 12 x 12 x 14 = 2,0162,016/194 = 10.39 11 lbs LA to Chicago $33.86

How does this apply to your business? As you can see in the example above, the cost of shipping a 2-lb package via Priority Mail more than triples with DIM rates! When calculating shipping costs, it’s important to take DIM into account, or you may be forced to deal with dissatisfied customers or a significant profit loss.

Quick Tips

• One cubic foot = 12″ L x 12″ W x 12″ H = 1,728 cubic inches

• All Flat Rate (Priority Mail and Express Mail) boxes are exempt from DIM weight

DIM weight is applied to Priority Mail and Parcel Post items larger than one cubic foot

• If the DIM weight exceeds 70 lbs, the price will be at the 70 lbs rate