Shipping isn't just about tossing a package in a truck and hoping for the best. To get it right, you need to understand the numbers that drive the industry—like DIM weight and billed weight. These metrics can make or break your shipping budget, so getting familiar with them is a game-changer.
Cracking the Code: What Is Dimensional Weight?
Dimensional weight, or DIM weight, is a pricing system that doesn’t just care about how heavy your package is—it also looks at how much space it hogs. This makes sense when you consider that shipping trucks and cargo planes don’t have infinite room. Carriers like FedEx, UPS, and USPS rely on this method to ensure they’re using space efficiently.
Before 2015, it was all about weight and distance—simple, but flawed. A huge, feather-light box took up just as much space as a small, dense one, but carriers were only charging by weight. That changed when major players introduced DIM weight pricing, making bulky-but-light packages more expensive to ship.
Dimensional Weight vs. Volumetric Weight—Are They the Same?
Yes. These two terms are basically twins, just with different names. No matter what you call it, the concept is the same: if your package is large but doesn’t weigh much, the shipping cost reflects the space it takes up rather than its actual weight.
To calculate DIM weight, you multiply a package’s length, width, and height, then divide by a specific number called the DIM factor. Each carrier sets its own DIM factor, meaning shipping costs can vary wildly depending on who you use.
Why Do Carriers Use Dimensional Weight Pricing?
Think of it like this: a truck full of pillows isn’t making the most of its capacity, even if it’s packed to the brim. Carriers need to charge for space, not just weight, to keep shipping profitable. That’s why lightweight but bulky packages often end up being more expensive than expected.
For compact, heavy shipments, you’ll probably be charged based on actual weight. But if your box is mostly air, DIM weight pricing ensures you pay for the room it takes up.
The DIM Factor: The Key to Shipping Costs
The DIM factor is the secret number carriers use to convert volume into billable weight. The formula is simple:
DIM Weight = (Length × Width × Height) ÷ DIM Factor
Each shipping company tweaks its DIM factor based on its own pricing model. USPS, for example, made a major shift in 2019, applying DIM weight to packages over 1,728 cubic inches—unless they qualify for flat-rate shipping.
How to Calculate Dimensional Weight
Measuring your package is step one. Get its dimensions in inches, then multiply them together:
Volume = Length × Width × Height
Next, divide that number by the carrier’s DIM factor. If the DIM weight is higher than the actual weight, you’ll be billed for the DIM weight. If the actual weight is higher, that’s the number you’ll pay for.
For example:
- Actual weight: 5 pounds
- DIM weight: 8 pounds
- You’re billed for: 8 pounds
But if the same box actually weighs 10 pounds, you’ll be charged for 10 pounds instead.
Optimizing DIM Weight Costs with ShipwithMina
Admittedly, dimensional (DIM) weight fees are like that sneaky extra charge you never see coming, and suddenly your shipping bill is way higher than expected. At ShipwithMina, we’re tired of seeing businesses get burned by it too. So, we use our massive shipping network that is seriously huge, to push for better DIM rates with carriers. Because we move so much stuff, we’ve got the kind of leverage that makes carriers listen. The result? You pay less to ship, and you stop getting blindsided by ridiculous charges.
But saving you money is just part of what we do. We also take a hard look at how you’re packing and shipping everything. Got boxes full of empty space? We’ll fix that. Sending light but bulky products and paying a fortune? We’ll help you rethink how it’s packed and which carrier makes the most sense. We’re all about making sure you’re not paying to ship air. And since we only win when you win, you’ll have a team in your corner that actually cares about helping you grow and not just one that throws you a rate sheet and calls it a day.
FedEx Dimensional Weight Rules in 2025
FedEx sticks with a DIM factor of 139, the same number they’ve used since 2017. That means a 10” x 10” x 10” package would have a DIM weight of:
(10 × 10 × 10) ÷ 139 = 7 pounds
If that’s more than the actual weight, you’ll pay based on the 8-pound DIM weight. FedEx’s base rates are closely matched with UPS, but slight price differences exist depending on the shipping zone—UPS might be cheaper in some areas, while FedEx wins out in others.
UPS Dimensional Weight in 2025
UPS uses a DIM factor of 166 for retail customers, but businesses with daily shipping rates get a lower factor of 139.
A higher DIM factor means lower shipping costs. Here’s how it plays out:
- Retail rate: (10 × 10 × 10) ÷ 166 = 6 pounds
- Daily rate: (10 × 10 × 10) ÷ 139 = 7 pounds
So, if you're a retail shipper, you might get a slight price break compared to daily rate customers.
USPS Dimensional Weight in 2025
USPS changed its DIM factor from 194 to 166 in 2019, bringing its pricing more in line with UPS. While this means slightly higher shipping costs for large packages, USPS still tends to be gentler on the wallet than FedEx or UPS when it comes to volumetric weight charges.
For example, a 12” x 12” x 14” box would be billed at:
- FedEx & UPS: 14.5 pounds
- USPS: 13 pounds (since (12 × 12 × 14) ÷ 166 = 12 pounds)
However, USPS applies dimensional weight pricing only for shipments going to zones 5 and higher. If you're shipping locally, you might avoid these charges altogether.
Cutting Down DIM Weight Costs
If your business deals with large but lightweight products, DIM weight pricing can be an expensive headache. The good news? There are ways to work around it.
One option is partnering with a third-party logistics (3PL) provider like ShipwithMina. These companies move high volumes of shipments, which gives them leverage to negotiate better DIM factors and volume discounts. That translates to lower shipping costs for you and your customers.
By using smarter packaging, working with fulfillment partners for ecommerce, and choosing the right carrier for your needs, you can keep DIM weight from eating into your bottom line—while still getting your products where they need to go.
