All Things Shipping
Apr 27, 2015

How Dimensional Weights Affect Shipping Pricing

Editors Note: This article has been updated to reflect the changed dimensional calculation formula for 2017.

There are four main criteria shipping carriers use to calculate shipping rates: package weight, package size, sender address, and recipient address. Let’s explore the two first criteria, weight & dimensions and demystify the concept of dimensional weight (DIM).

Back in the late fall, shipping carriers changed their rules, modifying their process for calculating shipping rates to use a package’s size rather than its weight. They call this hybrid concept dimensional weight. This new rule applies to most larger sized, lightweight packages containing items like backpacks, bike helmets, and footballs.

Shipping carriers are wise to saving space and cutting costs. Packages are shipped across borders in trucks, trains, and planes. The bigger the package, the more space it takes up and the less room there is for more packages. More bike helmets on a truck means lower volume of flatter packages and less profit for the carrier. Basing your shipping rate on box dimensions via dimensional weight pricing more accurately reflects the carrier’s true cost to deliver these larger packages.

Here’s how Dimensional Weight is calculated:

So why does this matter for your business? If you’re shipping larger, lightweight items, your shipping costs went up since dimensional pricing went into effect. If you want to pay less, be conscientious and optimize for box size. If you’re using Shippo’s discounted USPS rates, you’re already saving money, but why not save more by adapting your packaging?


Helpful Tips:

• DIM weight applies only for Priority Mail parcels exceeding 1 cubic foot (12x12x12in) and going to zones 5-9. Calculate zones here.

• All Flat Rate (Priority Mail & Express Mail) boxes are exempt from DIM weight.

• If the DIM weight exceeds 70 lbs, you’ll pay the 70 lbs rate.

Take Action: rethink the way you pack your orders. Use tighter-fitting packaging and fewer peanuts! If you’re willing to be even more flexible, try using padded envelopes or poly bags instead of boxes. For even more ideas, check out this article from

Shippo is a multi-carrier API and web app that helps retailers, marketplaces and platforms connect to a global network of carriers. Businesses use Shippo to get real-time rates, print labels, automate international paperwork, track packages and facilitate returns. Shippo provides the tools to help businesses succeed through shipping.

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Shan Lian
was a product marketer at Shippo.

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