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?

Three main reasons:

  • Major shipping companies, including FedEx, use dim weight to calculate shipping prices; this is called dim weight pricing.
  • Dim weight pricing may reduce shipping costs for customers who pack more efficiently. 
  • Reducing packaging can make shipments more environmentally friendly by helping lower fuel emissions, and can help you avoid overpacking, which wastes material. 


Imagine how often people ship using packaging that’s too big. To stabilize the contents, these oversized boxes must be packed with extra cushioning. These over-packed boxes fill shipping trucks with cubic feet of unneeded corrugated fiberboard, air pillows, and air cushioning. In some cases, people are literally paying to ship air.


Dim weight pricing can reward customers who eliminate extra, oversized packaging. By increasing the shipment density, we can often pack more products on our trucks and planes.


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

To calculate dim weight:

  1. Multiply 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 calculate the dim weight of your packages. Calculating dim weight can seem complicated, but using it correctly and right-sizing your packaging can save your business money -- and help protect the planet in the process.

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 packaging  size for your item. They can also help you determine how much cushioning is needed for delicate items, so you're not overpacking and wasting material, and you're not underpacking and risking damage.
  • Request a packaging design consultation with a FedEx packaging engineer. The packaging engineers will offer options that can help you:    
    • Improve packaging efficiency, which may mean less waste.
    • 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.