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Dimensional weight is one of those things that makes total sense once you stop thinking about it like a normal person and start thinking about it like a shipping company. It’s not about how much your package actually weighs—it’s about how much of the truck’s existential space it selfishly occupies.
This is why you can ship a brick and pay for a brick, but ship a giant box of packing peanuts and pay as if you’re mailing a small car. Canada Post, FedEx, and UPS calculate your cost based on whichever number is bigger: the actual weight or the imaginary, mathematical weight they assign based on volume. In other words, shipping rates don’t care about your reality. They care about physics, efficiency, and making sure a warehouse full of people in reflective vests don’t lose their minds trying to Tetris all these boxes into a truck.
Honestly, they’re the same thing, just with different names to keep things interesting. Both refer to the idea that shipping costs shouldn’t just be about how heavy a package is, but also about how much space it takes up—because apparently, empty air in a truck is the most expensive thing on Earth.
So, instead of just measuring how much your package weighs, carriers will look at its volume—length, width, and height—and calculate what it would weigh if it were made out of something dense. Then, they divide by a number (which is like the shipping company’s secret sauce) to come up with a “volumetric” or “dimensional” weight. It’s all about making sure the big, fluffy packages that take up a ton of room but don’t weigh much get charged just like the heavier ones. They’re basically trying to make sure that air doesn’t get a free ride.
The DIM factor is a number used by shippers to calculate the dimensional weight of a package. Essentially, it’s the divisor you use after calculating the volume of your package (length × width × height) to figure out how much space your package is taking up, rather than just how much it weighs.
Each shipping company—like UPS, FedEx, and Canada Post—sets its own DIM factor, and they like to mix it up a bit by updating it now and again. So, it’s kind of like a pricing refresh where they decide what number they’ll use to measure your package’s “space” value. Keep an eye on it, because that number directly impacts how much you’ll pay to ship your package.
It’s actually pretty straightforward, and here’s how you do it:
DIM weight = (Package Length × Package Width × Package Height) / Carrier’s DIM factor
Let’s break it down, shall we?
Grab your tape measure and measure the length, width, and height of your package in inches. Don’t cut corners—measure from the longest points on each side.
Multiply those three numbers together. This gives you the cubic size of your package. It’s basically the space your package occupies.
Take that cubic size and divide it by the carrier’s dimensional factor (the number they use to adjust based on their system). This factor can vary depending on the carrier, but no worries—we’ve got tools to help with that.
Now, compare the dimensional weight to the actual weight of the package. The carrier will go with the bigger number—because, you know, they want to make sure they’re not giving away free space.
It’s that simple! Just remember, dimensional weight is all about making sure you’re paying for the space your package is taking up.
