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What’s Dimensional Weight and How Is It Calculated? (Bonus: Free Dimensional Weight Calculator)

What’s Dimensional Weight and How Is It Calculated? (Bonus: Free Dimensional Weight Calculator)

Posted By
Austin Kreinz
January 5, 2023
Title asset to the "Summer Shipping" blog post from Atomix Logistics. A small green 3D truck with a small sun floating above it portrays the hot summer sun during order transport. KW: Ecommerce, 3PL, order fulfillment, fulfillment center, summer order fulfillment, new orders, new customer, temperature, protection, packaging, eco-friendly, sustainability

Carriers hate large packages that are lightweight. 

As such, in 2019 the 4 major carriers instituted a new law (so to speak) that penalizes packages that take up more space in their trucks than the actual weight. This is called DIM (or Dimensional) Weight.

But wait!

There are large fulfillment companies that have negotiated contracts, not just to lower rates, but to eliminate Weight Surcharges and DIM-Based Pricing. For example, a leading fulfillment service provider like Atomix, has a unique contract with UPS to avoid these extra fees, which in turn saves ecommerce brands hundreds of thousands of dollars a year!

So let’s learn everything about DIM Weight and how Atomix can reduce DIM weight surcharges.

Table of Contents

  1. What is Dimensional Weight
  2. How is it Calculated (Free Calculator Below!)

What Is Dimensional Weight?

Dimensional weight, also known as DIM weight or volumetric weight, is a formulaic pricing technique used by shipping companies to ensure they don’t lose money on large, lightweight shipments. The pricing structure for packages, now, takes into consideration the physical weight and the dimensional (e.g. size) weight.

We’ll get into the formula later on but basically it means you’ll be dealing with two different weights now: 

  • Physical, and
  • Dimensional.

Key: So, if your package is heavy or small, you really don’t have to worry about dimensional weight.  You’ll pay for shipping based solely on the actual package weight. 

To understand the impact of dimensional weight, let’s look at the difference between a large, fluffy pillow and a shoe.

  • First, a shoe weighs more than a pillow.
  • But, when it comes to dimensional weight, a pillow could be considered “heavier” because it takes up more space than a shoe.
  • As a result, carriers determine weight by whichever is greater - the physical weight or the dimensional weight - of the package.

How Is Dimensional Weight Calculated?


To calculate dimensional weight charges, use this formula:

  • For USPS (and DHL Ecommerce)

H x W x D/166 = DIM weight

  • For Fedex and UPS 

H x W x D/166 = DIM weight

Let’s say a box weighs 10 pounds. Your box is 20 inches x 10 inches x 4 inches. Multiply 20x10x10, which equals 2,000. So the DIM Weight is 13 pounds, which is greater than 10 pounds - the actual weight of the product. 

As such, USPS would use the DIM Weight of 13 pounds. 

Now suppose you could fit your items into a slightly smaller box? 

Specialized fulfillment providers like Atomix applies its expertise in shipping oversized boxes to help our clients with situations like this to avoid extra fees. If a product is on the line between dimensional and weight-based pricing, we will look for ways to reduce your shipping costs, by finding a smaller box or through packaging analysis.

Free Dimensional Calculator Process

Here’s a free calculator that you can utilize as we go through our example.

Calculating dimensional weight of a package consists of three steps:

Inputs - 

  1. Package Dimensions: Measure the length, width, and height of your package, using the longest point for each side.
  2. Cubic Size: Multiply the measurements to get the cubic size of your package.
  3. DIM Factor: Divide the cubic size by the DIM Factor*

Output - 

  1. Final Result: Round UP to the nearest whole number (12.3 is 13 pounds).

*Note - DIM Factor is a number set by postal carriers to represent the cubic inch per pound of a package. Only two numbers to remember:

  • FedEx, UPS, and DHL Express: 139
  • DHL eCommerce** and USPS**: 166

** Only Applicable if the package is larger than 1 cubic foot.


  1. Package Dimensions: 25 x 10 x 6 inches (Length, Width, Height). 
  2. Cubic Size: 1,440 cubic inches 
  3. DIM Factor: 166 for USPS packages
  4. Final Result: 20.24 is 21 Pounds

Depending on the carrier, you’ll divide the total cubic inches by the dimensional weight divisor. For FedEx and UPS, the retail dimensional weight divisor is 139 and both DHL and USPS use 166 as the dim factor for packages less than 1,728 cubic inches (or 1 cubic foot).

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