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.
What is 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.
- UPS: 139 for daily rates and 166 for retail rates
- FedEx: 139 for many U.S. package services
- USPS: USPS applies dimensional weight to certain package services, and its dimensional weight rules can change. Check the current USPS guide before using a USPS divisor in your calculations.
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.
Actual Weight vs. Volumetric Weight vs. Billable Weight
- Actual weight: What the package weighs on a scale.
- Volumetric weight: A calculated weight based on the amount of space the package takes up.
- Billable weight: The weight the carrier uses to rate the shipment, usually whichever is greater: actual weight or volumetric 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.
Volumetric Weight Comparison Table
| 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.
Why Does Volumetric Weight Matter?
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.
Making the Most of Volumetric Weight
While it may seem like an unwelcome facet of the shipping world, you can use volumetric shipping to your advantage by maximizing shipping efficiency.
- Efficient Packaging – Using the smallest possible box for every order is the first and most vital step in mastering the process. If you’re not already using one, you need a tool to automate the process and ensure every order goes in the correct box.
- Efficient Grouping – When shipping multiple products or orders simultaneously, you can leverage the system and create a single shipment that’s perfectly balanced in weight and dimensions. Pairing lower and higher-density items together can minimize any potential losses caused by volumetric weight rating. This is especially effective if you’re making large LTL freight shipments where many products are packed together.
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.
ShipperHQ’s Dimensional Packing Feature
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.
FAQs
What is the volumetric weight formula?
The volumetric weight formula is: length x width x height ÷ volumetric divisor. The divisor varies by carrier, service, rate type, destination, and unit of measurement.
How can retailers use volumetric weight to maximize shipping efficiency?
Retailers can use volumetric weight to improve shipping efficiency by choosing the smallest possible box for each order, reducing empty space, and automating the packing process so rates are closer to how orders actually ship.
How does volumetric weight impact return shipping and reverse logistics costs?
Volumetric weight can increase return shipping costs when returned items are packed in oversized boxes. When processing returns or managing reverse logistics, retailers should consider both actual weight and volumetric weight to estimate costs more accurately.
How does volumetric weight affect international shipping compared to domestic shipping?
Volumetric weight calculations generally apply to both international and domestic shipping. However, international shipping may also involve customs regulations, duties, taxes, and carrier-specific divisors, so it is important to verify the rules for each service and destination.
Are there exceptions where volumetric weight is not applied?
Some carriers may have exceptions or limitations for certain small, lightweight, or service-specific shipments. Because these rules vary, retailers should check with their carrier or shipping provider before assuming volumetric weight does not apply.
How can you save on shipping bulky items?
To save on shipping bulky items, choose right-sized boxes, reduce empty space, use efficient packing materials, group items intelligently, and negotiate carrier rates when possible. Reducing package dimensions can lower volumetric weight and help reduce shipping costs.
