Dimensional weight calculator (DIM weight)
See whether a carrier will charge you for the size of your box instead of its weight. Enter the box dimensions in inches and the actual weight in pounds, and get the dimensional weight and the billable weight.
Help: how to use it and FAQ
How to use it
- You enter the data
- Smallo works it out
- You get the result
- Choose the carrier rule or a custom divisor.
- Enter the length, width and height in inches and the actual weight in pounds.
- Read the dimensional weight and the billable weight the carrier will charge.
Frequently asked questions
What is dimensional weight?
It is a weight based on the size of the box: length × width × height in inches, divided by a number called the divisor. Carriers charge for whichever is greater, the actual weight or the dimensional weight.
Which divisor should I use?
UPS and FedEx use 139 for daily rates. Since July 2026, USPS also uses 139 for packages over 1 cubic foot. Contract or retail rates may use a different divisor, so check your carrier account.
How do I lower my billable weight?
Use the smallest box that protects the product, avoid empty space and filler, and consider poly mailers for soft items. Every inch you cut from a side reduces the volume.