What’s Dimensional Weight and How Is It Calculated?

Quick! Think of every shipping carrier’s mortal enemy. Is it a pile of bricks? A pet reptile being shipped across the country? Cartons of glass perfume bottles? While all of these options can be considered shipping nuisances, we often forget about the mighty but fearsome pillow. That’s right, this sleep essential, and products like it, can spell bad news for sellers and carriers alike. The reason behind this is something called dimensional weight, or DIM weight. 

Scratching your head? Worry not. In this article, we take you through the basics of dimensional weight: how it’s defined, when it’s applicable, and what you can do about it. 

What Is Dimensional Weight?

Let’s say you want to ship a pillow to your Aunt Janice in Idaho. Naturally, assuming you love your Aunt Janice, your pillow is soft, fluffy, and probably a decent size. While that all seems perfectly harmless, it’s a different story in the world of logistics. Similarly to how we try to take all the grocery bags from the car in one go, carriers want to cram as much as possible into one shipping container. So, something like your thoughtful gift to Aunt Janice actually takes up a lot of valuable real estate, most likely at the cost of other packages.

Dimensional weight — also known as volumetric weight or DIM weight — is a pricing technique used by shipping companies to ensure they don’t lose money on large, lightweight shipments. We’ll get into the formula in just a bit, but it basically means that you’ll be dealing with two weights now: physical and dimensional. 

We can all agree that a book physically weighs more than a pillow. But, when it comes to dimensional weight, the pillow could be considered “heavier” because it takes up more space than the book. When it’s time to ship out orders of books or pillows, carriers determine shipping rates by whichever weight value is larger, be it the DIM or physical weight of the package.

How Is Dimensional Weight Calculated?

Calculating dimensional weight of a package consists of three steps:

  1. Measure the length, width, and height of your package, using the longest point for each side.
  2. Multiply the measurements to get the cubic size of your package.
  3. Divide the cubic size by the DIM factor.

What’s the DIM factor, you ask? Unlike the X-Factor, you won’t have tingles of anticipation with this one. The DIM factor is simply a number set by postal carriers to represent the cubic inch per pound of a package. 

Luckily, there are only two numbers you need to know:

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

* Note: For DHL and USPS, DIM weight only applies if the package is larger than 1 cubic foot.

Let’s break this down with an example. Say you have a box that measures 40 in x 16 in x 16 in. 

If we multiply those three dimensions, we get 10,240 cubic inches. Now divide that by the DIM factor that your carrier uses. Let’s say you’re using FedEx to ship your package, so you’d divide by 139. The dimensional weight for your package is 10,240 divided by 139 which equals 73.67 lbs.

Now that you’ve got your DIM weight, compare it to the actual weight of your order — the larger of the two is what the shipping carrier will use to determine shipping cost. So, let’s say the actual weight of the package was 70 lbs. Since the DIM weight is higher, that’s what you’d be billed at.

PRO TIP! Make sure to always round up the results. Using the example above, the DIM weight value equals 73.67 lbs, so you would round up to 74 lbs.

Can Dimensional Weight Be Avoided?

To some degree, yes! If dimensional weight can’t be avoided, it can at least be reduced using these helpful tips: 

  • Try making your package as small as possible. Fulfillment companies (like us!) help sellers like you manage their shipments by providing packaging services that maximize space and reduce shipping costs. If you’re shopping around for fulfillment centers, this is definitely something worth mentioning.
  • Try looking for alternative services that have a more advantageous formula. You know what they say — no dimensional divisor is created equally! At least, we think that’s how it goes. Regardless, we encourage you to shop around. With all the different shipping options available, you’ll be sure to find the best fit for you and your business.

While dimensional weight can be a little pesky, without it, freight companies wouldn’t be able to maintain their stellar service. When it comes to shipping and logistics, functionality is king. A package that is large but light (like a box of pillows) takes up more space than one that’s small but heavy (like a box of books), so dimensional weight comes in to ensure fair charges and optimal efficiency when shipping. Although it takes some trial and error, with the right strategy, your savings will add up!

BONUS! Don’t like math? We have you covered! Our handy DIM weight calculator makes estimating the cost to ship a package a breeze. Simply plug in the dimensions and actual weight of your package, and we’ll give you the base cost to ship it by carrier.