Dimensional Weight: Why it Matters and How to Calculate

Whether you ship packages for your online business or for yourself, dimensional weight is the major factor in the shipping rates.
When sending a package, you must have had such confusion. Why the actual weight of the package is 10 pounds, but the final shipping cost is calculated by 15 pounds?


This is because most of the shipping carriers charge shipping rates for larger and lighter packages to help cover the cost of storage space in transit. 

Dimensional weight is the major factor in the shipping rates. Whether you ship packages for your online business or for yourself, we'll help you understand and take advantage of DIM pricing from USPS, FedEx, and UPS.


What is Dimensional Weight?

Dim weight is the amount of space a package occupies in relation to its actual weight. 


  •  Dimensional Weight is the amount of space a package takes up in a truck or airplane during transit.
  •  Dimensional Weight Pricing charges a higher rate for larger packages that are very light in weight.
  • Dimensional Weight Pricing only applies to packages larger than 1 cubic foot.
  • Most e-commerce packages are smaller than 1 cubic foot and are not subject to Dimensional Weight Pricing.


Because of the limited space on the delivery truck, the dimensional weight takes into account the package density to determine shipping costs. 

Top carriers such as USPS, FedEx, and UPS calculate shipping rates based on the larger number: the actual weight of the package or its calculated volumetric weight. For each shipment, you are charged based on the dimensional weight or actual weight of the package—whichever is greater.


What is Dimensional Weight Pricing?

The purpose of dimensional weight pricing is to calculate USPS, FedEx, and UPS shipping costs, taking into account the amount of space a package takes up, and charging accordingly. 

Due to the rapid growth of e-commerce shipping, the amount of space each package takes up is very valuable.

Generally speaking, if your package is heavy but small, you do not need to worry about DIM pricing. You will only pay the carrier shipping rates based on the actual weight of the package. However, if you ship relatively light items in large boxes, you may pay more than you would normally expect due to DIM weight pricing.


How to Calculate Dimensional Weight Pricing?

The dimensional weight calculation uses a formula to determine. That formula rounds each measurement to the nearest whole inch.

Note: For non-square packages, you would take the longest dimension on each side and round up.


This is the DIM weight formula:

DIM weight = package length in inches x package width in inches x package height in inches / DIM divisor

The DIM divisor for FedEx and UPS is now 139.

For example, let's say you have a package with dimensions of 15" x 15" x 8". Multiply these dimensions together to get 1,800 cubic inches. To determine FedEx's dimensional weight, you simply divide the total cubic dimensions by 139. So, in this case, the volumetric weight would be 1800 / 139 = 12.9 lbs.

This means that when shipping this package, you will be charged a minimum of 13 pounds (carrier rounds up to the nearest pound). If the weight of the package happens to be more than 13 pounds, you will be charged for the actual weight of the shipment. If the actual weight is less than 13 pounds. For example, assuming it is 10.5 pounds, then the dimensional weight will apply and you will be billed at 13 pounds.

How to Minimize the Impact of Dimensional Weight?

If dimensional weight is hurting your bottom line, here's some tips to minimize its impact.

Minimize wasted space

Using the previous example, perhaps the shipper who used the 15" x 15" x 8" box was only doing so for convenience. Upon further investigation, he discovered that the product would actually fit in a 15" x 15" x 5" box. Therefore, the seller could have lowered the height of the box by 3" and maintained the same DIM weight.

Use More Standard Size Box

If you only have one size of box to choose from, it will be difficult to package effectively. On the other hand, having too many sizes of boxes makes it difficult to choose the right size box for an order and also requires you to stock more packaging materials. Many distributors find that a good balance of 10-20 different box sizes can be achieved.

Looking for Alternative Shipping Options

FedEx and UPS are the two largest carriers in the world, however, they are not the only ones.

An obvious alternative is the United States Postal Service (USPS). If you sell fairly lightweight, bulky items, USPS may be your best choice.

USPS currently has different DIM weight rules than FedEx and UPS. For USPS, if a package exceeds 1 cubic foot, it is subject to dimensional weight and applies to shipments to all regions. In addition, USPS has a DIM divisor of 166.

Final Words

To help our customers with their dimensional weight challenges, ShipSaving offer the best shipping rate tool that automatically selects the most economical shipping method and carriers for each of your order.

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