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What Does Dimensional Weight Mean in Shipping? Guide for E-Commerce Businesses

Dimensional weight (sometimes referred to as just “dim weight”) refers to how one-way shipping prices are calculated. Dimensional weight is based on the cubic area (a.k.a. volumetric weight), not on actual weight in ounces or pounds.

Using dimensional weight rates costs e-commerce businesses money if they ship a high volume of lightweight goods. Why? When given a choice between charging for the dimensional weight or the weight of a package, the carrier always demands the higher price of the two.

Shipping carriers use dimensional weight because many lightweight, but bulky items take up excessive space on transit vehicles, so they need to make up for the loss in income that they’d receive from heavier, but less bulky items (smaller, denser parcels).

Now, with the shipping crunch exacerbated by the pandemic, carriers are more pressed than ever to make the most out of every trip their trucks or airplanes run. Hence, the reason for dimensional weight.

Knowing how to navigate the nuances of dimensional weight shipping can reduce shipping costs that cut into your business’s profits, which is why we created this guide. Keep reading to learn what online retailers need to know about dimensional weight, including:

How to Calculate Dimensional Weight for Shipping E-Commerce Orders

Dimensional weight rates are based on cubic area, which is the length times the width times the height of a shipping box. That cubic area is then divided by a “dim divisor” to calculate the final shipping cost for a parcel.


It’s important to note that the DIM divisor varies by carrier. FedEx and UPS have a DIM of 139, whereas USPS has a DIM of 166.

How Does Dimensional Weight Affect Shipping Costs?

Once you understand how dimensional weight works, it’s easy to see how it may seriously impact shipping costs.

For example, if you sell small glass items that require a large amount of protective packaging, such as light bulbs or glass cups, your shipping expenses may be higher with dimensional weight rates–even though the merchandise isn’t heavy at all.

Many online retailers wind up getting charged by dimensional weight rather than actual weight because of how their items are packaged (not always within their control) or how multiple items in an order are combined.

For example, you’ve probably gotten a package from Amazon or another e-commerce site with a bunch of small items grouped in the same box, surrounded by bubble wrap or bubble cushion.

Many health and beauty items are packed this way, as well as computer and automotive parts, optics (including eyeglasses), personal electronics, kitchenware, and decorative objects, to guard against damage resulting in returns and unhappy customers.

Best Practices for Dimensional Weight and E-Commerce Shipping

The higher your total parcel volume, the more essential it is to get shipping costs under control. Even if each box costs you a few extra cents, that can add up to hundreds or thousands of dollars in a short time, thereby eating into your profit margins. In addition, since the advent of dimensional weight rates, e-commerce vendors also need to consider package area, as well as weight, which compounds the challenge of economical shipping.

There are some things you can do, though, to lower costs:

Understand how shipping costs with your carriers are calculated, and plan your order packing accordingly.

Are your carriers using dimensional weight rates? What is the dim divisor? Can you shop around for a carrier with better rates?

For small packages under one pound for which you’re paying by actual weight, do they charge by the ounce? How do they round up? For instance, if you have a 17-ounce parcel, do they charge you for 17 ounces or two full pounds, because it’s over a pound? What is the criteria for extra large packages by weight or dimensions?

Know how shipping zones work.

Shipping zones are geographical boundaries that represent the distance a parcel travels when shipped. In the U.S., a package on one coast can travel across several of the eight zones to reach the opposite shore. Most carriers charge by how many zones you cross for each parcel’s actual or dimensional weight. If you can reduce the number of zones traveled–for instance, by having distribution centers in various zones–you can lower your shipping costs.

Use the least amount of protective packaging possible.

Of course, you have to safeguard the contents of your boxes. Still, you have to find a happy medium between wasteful extra packing material that drives up dimensional weight costs and insufficient protection, resulting in damaged goods.

You may have to think strategically when packing multiple items in one box. The idea is to save on space if you’re being charged dimensional weight rates, but you must keep your packing process streamlined to meet promised delivery times.

For example, for items that often ship together, such as popular candles and perfumes, can you slot them together in your warehouse for easy picking and wrapping together versus individually?

Don’t forget about the dimensions of your boxes. First, is the overall size of your parcels typically too large, causing you to use a large amount of cushioning to fill space? In that case, you can consider downsizing your boxes. Denser packages nearly always cost less to ship these days.

Second, are you using thicker boxes than you need to? An eighth of an inch difference doesn’t sound like much, but times three for each parcel (length x width x height), multiplied by your total number of parcels adds up quickly. Be aware that the measurements printed on the bottom of the box are usually for the inside of the box, not the outside, which is what the shipping carrier measures. The thicker the corrugated cardboard, the greater the difference between the interior and exterior dimensions.

Review the need for packing efficiency with employees.

If you are doing a lot of manual packing, workers must understand how you are paying for shipping and what to do to cut costs. If you have a standard “this item always ships in this size box” policy, make sure packers know to do this without exception.

Consider incorporating extra shipping costs into the price of your merchandise.

Since the pandemic began and online sales became even more competitive, shoppers expect free shipping on most items. If you find yourself paying too much for shipping, rather than charging for shipping, raise the price of your merchandise to include the shipping cost.

It’s a psychological thing, but consumers would rather pay more for an item and get free shipping than the other way around.

It might sound crazy, but given that the number one reason for cart abandonment is due to shipping-related issues, such as high shipping costs, it’s worth evaluating.

Outsource orders to a fulfillment partner that is well-versed in the nuances of dimensional weight shipping.

If navigating dimensional weight shipping sounds like a headache, there is an easy alternative: collaborating with an e-commerce fulfillment partner.

An e-commerce fulfillment partner can store your inventory, receive orders, pick and pack parcels, and manage all the shipping logistics–including finding the most cost-effective packaging and carriers.

The best fulfillment centers also provide other business-boosting services for e-commerce, such as:

Optimize Dimensional Weight Shipping with GLF E-Commerce Fulfillment

Are you spending too much on shipping? Lost when it comes to calculating various packaging materials or dimensional weight costs?

With 20 years of experience in fulfillment, packaging, shipping and more, GLF can create a custom solution for your business that saves money and expedites delivery times. Take this free fulfillment assessment to see if partnering with GLF is right for your business.

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