In the business of eCommerce, few details are as crucial to get right as shipping rates.
But without accurate dimension and weight information, you may be paying too much or charging customers too little. Volumetric weight can help you unlock more accurate rates, improve packaging, and protect your margins.
Quick answer: Volumetric weight, also called dimensional weight or DIM weight, is a shipping calculation based on package size instead of scale weight. To calculate it, multiply length x width x height, then divide by the carrier’s volumetric divisor. Carriers usually charge based on whichever is greater: actual weight or volumetric weight.
Volumetric weight is a specific shipping measurement that determines the density of a package by incorporating both dimensions and weight. Also called “dimensional weight,” the number comes from a simple volumetric weight calculation formula: take the volume of a package, then divide it by a “dimensional divisor.”
Volumetric Weight = (Length x Width x Height) ÷ Volumetric Divisor
The industry standard dimensional divisor, sometimes called a volumetric divisor, is often 139 for many U.S. parcel rating scenarios, but carriers may use different formulas based on rate type, service, destination, unit of measurement, or contract.
Important update: UPS and FedEx now round fractional package dimensions up to the next whole inch before calculating dimensional or volumetric weight. That means a box measuring 9.1 inches may be treated as 10 inches for rating purposes.
That number is compared to the package’s actual weight. Whichever number is higher is used as the billable weight.
This is why a lightweight but oversized box can cost more to ship than a smaller, heavier package. Carriers are not just charging for pounds. They are charging for the space that shipment takes up in a truck, plane, or delivery van.
| Carrier | Common Volumetric Divisor | Applicable Services | DIM Weight Calculation |
| UPS | 139, daily rates | Many U.S. package services | (Length x Width x Height) ÷ 139 |
| UPS | 166, retail rates | Some retail rate scenarios | (Length x Width x Height) ÷ 166 |
| FedEx | 139 | Many U.S. package services | (Length x Width x Height) ÷ 139 |
| USPS | Varies by service and current USPS rules | Certain package services | Check the current USPS dimensional weight guide before rating |
Example: An 11 in x 8 in x 9 in package has an actual weight of 4 lbs. But it would be rated on its dimensional weight of 6 lbs. We find this number by calculating: (11 x 8 x 9) ÷ 139 = 5.7, rounded up to 6 lbs.
Most importantly, you need to know the volumetric weight of your packages so you can charge customers the correct rates. Your carriers are already using volumetric calculations to determine transport costs. Because of this, you need to be aware of them as you build them into your shipping strategy and pass them on to buyers.
High-Density Items: If you regularly ship small but high-density items, you may not be too affected by dimensional or volumetric weight.
Example: A textbook retailer ships out a single book. The book’s dimensions are 10 x 12 x 3, and its actual weight is 8 lbs. To find its dimensional weight, we calculate:
(10 x 12 x 3) ÷ 139 = 2.58 lbs, rounded up to 3 lbs.
While its volumetric weight is less than its actual weight, carriers will charge the greater of the two, returning a rate based on actual weight.
Low-Density Packages: If you regularly ship low-density items, you may be surprised by how much dimensional rating is actually costing you, even though it might seem like they’d ship at a lower cost. To compensate for lost space on low-density items, carriers must charge appropriately to remain profitable. They use the dimensional weight to account for the space taken up by large items, which could potentially be used to carry heavier, more cost-efficient shipments.
Example: A commercial foam retailer needs to ship three XL bags of bean bag filling to a customer. The bags go in a box that measures 24 x 24 x 24 and weighs 5 lbs.
(24 x 24 x 24) ÷ 139 = 99.45 lbs, rounded up to 100 lbs.
Its DIM weight calculations show a volumetric weight of 100 lbs., far higher than the actual weight. The carrier will rate based on the volumetric calculation to account for the cost of carrying a large, low-density item.
While it may seem like an unwelcome facet of the shipping world, you can use volumetric shipping to your advantage by maximizing shipping efficiency.
For B2B or bulk ecommerce orders, volumetric weight gets even more important. A single customer order may include multiple units, mixed product sizes, or several cartons. In those cases, the right packing logic helps determine whether items should ship together, separately, or through freight so the rate reflects how the order will actually leave the warehouse.
If you’re struggling with dimensional or volumetric weight calculations, it’s time to find a solution to automate the process. Our full-featured shipping management platform has a built-in feature to help with efficiency in packing and rating.
When you integrate your store with ShipperHQ, your orders will automatically be rated and packaged most efficiently. This way, you’re less likely to ship orders in oversized boxes. You’ll also have full transparency into the dimensional weight of your shipments, reducing the chance you’ll be charged more than expected for a shipment.
Because most e-commerce platforms don’t have dimensional rating capability built-in, retailers need solutions like ShipperHQ to master the complex requirements of business shipping. See how our intelligent shipping logic can transform your shipping experience, and your store, starting today.
Find a full rundown on dimensional shipping, and get started with a free trial today.