Dimensional Weight: What Is It?

Learn why dimensional weight matters and how you can avoid it
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Let’s talk about one of the most confusing terms in the shipping industry: dimensional weight. Dimensional weight is like a snake in the grass, waiting to ambush you when you least expect it! Seriously, though: it’s something to always be aware of when shipping packages. The costs associated with dimensional weight are astronomical, but can easily be avoided with a little bit of planning. The problem is, most people don’t know dimensional weight exists, let alone know what it is. Lucky for you, we’re here to shine some light on it. This article is all about what it is, how it’s calculated, and how you can avoid it. If you’re ready to roll up your sleeves, let’s get started!

Understanding Dimensional Weight

Dimensional Weight (or “DIM,” for short) reflects the amount of physical space a package takes up in relation to its actual weight. Typically, shipping carriers apply dimensional weight costs to larger packages that are lightweight. In that regard, dimensional weight is in essence a penalty for weight-based shipments that are oversized. Some examples of when you’ll get hit with DIM charges include shipping wreaths or shipping pillows or bedsheets.

If you’re saying, “Huh?” to yourself right about now, you’re probably not alone. Let’s break it down as simple as possible. It helps to think of dimensional weight kind of like paying for a seat in a movie theater. You can’t exactly buy a single ticket and then demand a whole row to yourself on opening night. The movie theater needs to make money off those seats, so the only fair way for you to take up all that space is to pay for each seat. Well, that’s pretty much what dimensional weight is. In a nutshell, you’re paying for the extra space that your package doesn’t need to be taking up.

Why It Matters

Understanding DIM is important when you’re shipping a larger-sized box because the cost is sometimes greater than the actual weight of the package warrants. Needless to say, you don’t want to be on the wrong end of that equation. This especially matters if you’re running your own E-commerce business! Shipping costs are often an E-commerce business’ biggest expense outside of costs of good sold. It’s crucial to keep those costs as low as you possibly can, and avoiding paying for dimensional weight is one of the best strategies to do just that.

We’ll admit it: dimensional weight is confusing. However, if you understand everything we’ve talked about so far, then you’re officially miles ahead of most small businesses! Hang in there—we promise it’s worth it.

Pro Tip: All the carriers will determine the price of your postage based on your package’s actual weight or its dimensional weight. They’ll end up charging you whichever number is greater! UPS and FedEx apply dimensional weight to both domestic and international shipments, while USPS only applies it for domestic packages.

Why Do the Carriers Use Dimensional Weight?

Since most of the shipping carriers’ services are weight-based, large carriers like UPS and FedEx apply DIM so they don’t lose money transporting large, lightweight packages that take up excess space in their trucks. The real estate inside those trucks is valuable, and if the carriers aren’t making money off of it, that money has to come from somewhere else. That’s exactly where dimensional weight comes into play.

For example, if you were shipping a large box full of nothing but packing peanuts, you would think your shipment would be relatively inexpensive, since the weight of the package itself was very light. However, the box would take up a lot of space on the truck, making it an expensive use of space for the carrier. This poses a problem for all of the carriers, and they solve that problem with dimensional weight. Therefore, the dimensional weight is used as the billing weight when it exceeds the actual weight of the parcel.

Pro Tip: A lot of beginners mistake dimensional weight for Priority Mail Cubic, a “secret” discounted USPS mail class where the price of postage is based on a package’s outer dimensions and not its weight. In reality, DIM and Priority Mail Cubic have NOTHING to do with each other. Learn how to choose the right USPS mail class.

How Is Dimensional Weight Calculated?

Dimensional weight is calculated by multiplying a package’s length, width, and height, then by applying a volumetric divisor to the resulting number. To find the dimensional weight of a package, follow these steps:

  1. Figure out the cubic size of the package. Round each measurement of your package to the nearest whole inch, and then multiply the package’s length by width by height (for example, if the package width is 12.53, round it up to 13; if it’s 12.49, round it down to 12)
  2. Determine the weight. Weigh the package on a scale and again, round up to the next whole pound.
  3. Determine DIM. Divide the cubic size of your package by the volumetric divisor*. Round up to the next whole pound.
  4. Determine the billable weight. Compare the actual weight to the dimensional weight. The greater of the two will be the billable weight. If you have multiple packages, the billable weight will be the total of all the packages.

*Volumetric divisors vary based on which carrier you go through. Starting on June 23, 2019, USPS’ volumetric divisor for domestic packages will be changed from 194 to 166. UPS, FedEx, and DHL’s volumetric divisor is 166.

Note that some carriers still apply DIM weight to international shipments! For instance, UPS applies DIM charges to international packages, and uses 139 as their volumetric divisor (so, DIM charges on international packages becomes even more expensive).

A Quick Example

Although the volumetric divisor will soon be uniform across all shipping carriers, USPS was more favorable than FedEx and UPS when it comes to dimensional weight. USPS had used 194 for their divisor in the past, which was much more competitive than the other carriers (UPS and Fedex use 166 for their volumetric divisor, which was less favorable at the time). Even more competitively, however, was that USPS only applied dimensional weight pricing to packages in zones 5-9. However, this isn’t the case anymore. USPS now uses 166 as their divisor, and dimensional weight no longer takes the different zones into account.

Let’s say you have a package that measures 13″ x 13″ x 13″. Multiply the three dimensions to get 2197, and then divide that by 166 to get 13.23. That number is the dimensional weight of your package. So, if your package’s actual weight was less than 13.23 pounds, you’d get charged the 13-pound Priority Mail rate for zones 5-9. If your package was more than 13.23 pounds, the dimensional weight would be disregarded and you’d just be charged the actual weight.

Dimensional weight can make it more expensive to use Priority Mail for a large box than it would be if you used Parcel Select Ground, but Priority Mail is a much faster service and includes $100 of insurance with USPS shipping software.

Learn more about how USPS calculates DIM.

How Can I Avoid Dimensional Weight Charges?

Most people aren’t even aware that DIM even exists, so those costs creep up on them when they least expect it. Believe it or not, most shippers just find random boxes and throw their products in them without a second thought. Needless to say, those boxes are often way too big for their contents, so it’s not uncommon for them to be charged based on dimensional weight.

Fortunately, you can avoid DIM charges simply by planning! To speak frankly, you’re more likely to be hit with DIM penalties when you don’t put any thought into planning your packaging. It may sound like an obvious statement, but it’s critical to make sure your packaging always makes sense for your contents! For example, if you’re shipping a water bottle, don’t ship it in a huge box. Pretty simple, right?

Pro Tip: Planning your packaging strategically can also save you a ton of money! Shipping costs are often an E-commerce business’ biggest expense, and your package dimensions can be the difference between your business sinking or swimming. This is especially true for the USPS mail class Priority Mail Cubic. If you’re interested in optimizing your package dimensions, this Smart Cubic Calculator is a great place to start.

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