A  woman packing clothing into a brown FedEx box.

What is dimensional weight?

What is dimensional weight?

What is dim weight?

Dim weight is the amount of space a package occupies in relation to its actual weight. For each shipment, you are charged based on the dimensional weight or actual weight of the package—whichever is greater.

Why is dim weight important?

The short answer:

  • Major shipping companies, including FedEx, use dim weight to calculate the price of shipping, called dim weight pricing.
  • Dim weight pricing reduces shipping costs for customers who pack more efficiently.
  • Efficient packing can help to reduce fuel emissions.


Imagine how often people ship using packaging that’s too big. To stabilize the contents, these oversized boxes have to be packed with extra cushioning. These boxes fill up shipping trucks with cubic feet of unneeded cardboard, packing peanuts, and bubble wrap. In some cases, people are literally paying to ship air.


Dim weight pricing rewards customers who eliminate extra, oversized packaging. It increases the shipment density. And by increasing package density, we can pack more products on our trucks and planes, reducing fuel emissions by decreasing the number of trips. This makes it cost less to ship each package.


Image of a brown FedEx box showing how to calculate dimensional weight and the equation: LxWxH/139 = total cubic square inches

Dim weight is calculated by:

  1. Multiplying length by width by height in inches. Round each measurement to the nearest whole inch. The resulting total is the cubic size of
    your package.
  2. Dividing by 139 for U.S., Puerto Rico, and international shipments.


Need a little help with the math? Check out this dimensional weight calculator designed to help you easily calculate the dim weight of your packages. Calculating dim weight can seem complicated, but using it correctly and right-sizing your packaging will save your business money.

How can you right-size your packaging and save?

Here are some tips: 

  • Choose packaging to match the size and fragility of your item.
  • Explore other options like padded or poly mailers.
  • Bring your items to a FedEx Office location where a team member will professionally select the right-size packaging for your item. They can also help you determine how much cushioning is needed for delicate items.
  • Request a packaging design consultation with a FedEx packaging engineer. The packaging engineers will offer options that can help:    
    • Improve packaging efficiency.
    • Prevent damage to your product.
    • Potentially reduce shipping supplies costs.

Additional information

For additional information on the best way to optimize your packaging, check out our How to pack basics and guides page.