In Parcel Shipping, Size Matters Author: Jared Fisher
August 04, 2020

Editor's Note: This post has been updated with new links and content.
Original Publication Date: April 1, 2016

Today we’re discussing dimensional weight, an important topic for shippers and anyone involved in the supply chain.

But before we get into what dimensional weight is, let’s start with how shipping rates are calculated and the variables involved.

Variables in Shipping Rates

The first variable is the service level. That can be ground or a multitude of air services. There's next-day, second-day, and three-day select with some carriers.

Second is the zone, which factors in the origin zip code along and the destination zip code. And finally, you've got the weight. And that can be the actual weight or the dimensional weight of the package.

To summarize, the three shipping rate variables are:

  • Service level
  • Zone
  • Weight

How is Weight Calculated?

There are a few different ways that carriers look at weight. Most carriers take the actual or physical weight of the package, which is what we consider billable weight. That’s where the difference between the actual weight and the dimensional weight becomes important.

Unlike the actual weight of the package, which is the weight that you would see if you put it on a scale, dimensional weight looks at the package density and how much space the package will take up in the package car.

Dimensional Weight Formula

Dimensional weight is calculated as length times width times height divided by a DIM factor. The published DIM factor for FedEx and UPS right now, for example, is 139.

So you take the length times the width, times the height, divide that by 139, which is the published DIM factor and you'll get a number, which the fallout of that is what they would consider that the DIM weight.

In other words, dimensional weight measures the package density, which is the amount of space that the package will occupy. This is important for things like packing package cars, loading airplanes or managing the feeder network.

Why is Dimensional Weight Important?

Let’s look at an example. Maybe you want to ship a coffee cup, and you put it in a massive package. The parcel may only weigh two pounds, but it takes up the space of a refrigerator box.

Dimensional weight is the carriers’ way of billing for that extra space, and also incentivizing shippers to use the most efficient packaging possible.

Common Mistakes Calculating Dimensional Weight

One typical mistake we’ve seen is that customers don't know what the DIM factor is. They might think that there's a different DIM factor to use.

The biggest mistake, however, is usually when a customer looks at the bottom of the box or the carton that they're using and they use the dimensions that are stamped on the bottom of the box to calculate the dimensional weight without measuring the outside of the box. The dimensions on the bottom of a box are actually the internal dimensions so that customers know exactly what fits inside.

If you were to measure the outside of the box, depending on the size or the type of corrugate you're using, those dimensions can be off by a quarter-inch to a half-inch. In short, your box probably a different size than the dimensions stamped on the bottom.

If you’re looking at a 12 x 12 x 12 box and think that that’s what it will ship at because that's printed on the bottom, that’s usually not the case.

Most likely that box will be 'dimmed out' closer to 13 x 13 x 13 because the carriers are scanning the outside of the box, not the inside.

Does Dimensional Weight Apply to All Services?

Every service, including the final-mile delivery services that UPS and FedEx offer through SmartPost and SurePost, are subject to dimensional weight.

If you’re shipping ground, air, or postal hybrid, dimensional weight will be a factor.

How Has Dimensional Weight Changed Over the Years?

In recent years the carriers have lowered the DIM factor a few times. A few years ago it was actually 166, and the carriers recently moved it down to 139. Obviously, if you decrease the DIM factor, the dimensional weight will be higher. Dividing by a smaller number gives you a higher dimensional weight for a package with the same billable weight.

Also, dimensional weight didn't always apply to ground shipments. It started with air packages, and ground was not subject to DIM. When the carriers started applying ground dimensional weight, neither carrier applied it to the postal-hybrid services.

After a while, however, UPS and FedEx both decided that every package shipped through their networks would be subject to DIM. In short, the carriers seem to be looking for additional ways to apply DIM, number one, and then bill it at the highest weight possible.

The Future of Dimensional Weight

Lots of shippers assume that the carriers will lower the published dimensional factor down again.

It will probably be closer to 100, or “one,” but less than 139. It might not happen in the next couple of years, but at some point, it will probably be reduced at least one more time.

That said, as the DIM factor drops, shippers should remember that everything, including dimensional weight, is negotiable.

Negotiating Dimensional Weight

Your ability to negotiate DIM factors will vary depending on how much they impact your package characteristics.

If you aren’t overly impacted by the published DIM factor, for example, then it might not necessarily be too much of an issue. If you are being impacted, however, and the actual weight in your average build weight is off by more than 2-2½ pounds, it would probably be wise to reach out to the carrier and ask them if they can help with your DIM factor.

Minimizing the DIM Impact

Shippers can try other methods to minimize the impact of dimensional weight aside from negotiating a custom DIM factor. One option is to audit the corrugate you're using.

A lot of customers who reuse inbound boxes, for example, think they're saving money. But the dimensions of a reused box are often greater than the billable weight or the actual weight of the package would be. In other words, you’re saving dimes but spending dollars.

dimensional weight dim weight lojistic

The best thing to do is look at your corrugate, and if you have the opportunity to reduce the size of the boxes you're using, do it. In addition to negotiating a better DIM factor, those are the best two ways to start minimizing the impact of a DIM.

For more information on joining the thousands of businesses currently using Lojistic to help monitor, manage, and reduce their shipping costs, please click here.

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