What Is USPS Priority Mail Cubic? (All You Need To Know)

If you are a small business owner or hobby seller, you might always be on the lookout for ways to save money on postage. The United States Postal Service is quite attuned to that, and it offers many different mail classes and services to help keep costs down.

One such mail class is Priority Mail Cubic. What is Priority Mail Cubic and how can it save you money on shipping? I’m glad you asked – see below for your answer!

What Is USPS Priority Mail Cubic In 2024?

USPS Priority Mail Cubic is a special offshoot of Priority Mail shipping that allows qualified customers the option to ship based on the size of the package and the distance it’s traveling as of 2024. There is a 20-pound weight limit and a 0.5 cubic foot maximum, and customers typically ship at least 50,000 parcels annually.

To learn more about how Priority Mail Cubic works, how it’s priced, how fast it is, and much more, keep reading because I’ve got all you need to know!

Who Can Use USPS Priority Mail Cubic?

According to Shippo, it’s only available to specific customers who meet a 50,000+ annual package threshold (though Shippo customers have access to it, too).

Also, with the 20-pound weight limit and 0.5 cubic foot restriction, Priority Mail Cubic is best for medium-to-high volume shippers who deal in small but heavy goods (heavy relative to size).

Parcel Requirements

As I mentioned, packages going Priority Mail Cubic cannot weigh more than 20 pounds, and they must be less than 0.5 cubic feet.

Moreover, they cannot be any longer than 18 inches, and according to Shippo, the sum of the two longest dimensions cannot be more than 36 inches.

Further, tubes and rolls are not qualifying packages, but envelopes can be, provided they meet the other requirements.


Priority Mail Cubic is priced based on the size (of the box) and the parcel’s distance.

So, once you figure out your package’s size (actually volume, hence the term cubic), you include the distance it must travel, using Zoned pricing, just like Priority Mail.

To figure out your box’s volume, you take the measurements and round down to the nearest quarter-inch. After that, multiply length, width, and height; then divide that sum by 1,728.

What you are left with is a cubic value. Therefore, you can take that cubic foot measurement and apply it to the Pricing Chart listed here.

With that, notice how there are five tiers, one for each additional cubic tenth; each tier means “the cubic foot up to this size” – so Tier .2 means packages bigger than .1 and up to .2.

Additionally, you can use the USPS Zone calculator to figure out which Zone your destination resides in; remember, Zones are completely relative to wherever you are.

So, a parcel in Sarasota under the same cubic tier as a parcel in Baltimore will not find Austin, Texas, under the same Zone and will have a different price.


In addition to offering customers vastly discounted shipping rates, you receive the same shipping speed as Priority Mail – one to three days!

Plus, Cubic comes with included insurance (up to $100 in value) and free tracking.

What Is USPS Priority Mail Cubic Pricing?

What Is USPS Priority Mail Cubic Pricing?

USPS Priority Mail Cubic Pricing is calculated using the volume of the parcel (cubic feet) and the distance it is traveling.

That said, this is in contrast to regular Priority Mail, which relies instead on weight and distance.

To calculate the volume in cubic feet, round your height, length, and width down to the nearest quarter-inch and multiply all three measurements, as mentioned above.

Overall, you’re saving over 40% with Priority Mail Cubic; this is why USPS only offers this service to specific customers who ship 50,000+ parcels per year with the company.

How Fast Is USPS Priority Mail Cubic?

Priority Mail Cubic combines the benefits of discount shipping with Priority Mail speeds.

Priority Mail is, after all, the second-fastest domestic shipping option offered by USPS, taking between one to three days, depending on the distance.

Also, you get all the additional services of Priority Mail, including tracking and insurance.

Can Anyone Use USPS Priority Mail Cubic?

USPS Priority Mail Cubic is not available to just anyone.

Instead, the Postal Service offers this discount shipping class to medium-to-high volume shippers of 50,000 parcels or more per year.

Obviously, if you’re shipping this much, you are giving the Postal Service a great deal of business – you’re a terrific customer!

However, if you don’t ship that much, you can still access those rates. For example, by using a third-party postage seller like Shippo, you can get access to Cubic rates.

What Is The Difference Between Priority Mail & Priority Mail Cubic?

Priority Mail Cubic is a sub-service of regular Priority Mail, offered to a select group of customers who ship more than 50,000 parcels per year.

With that, Cubic can net customers discounts up to 89% off regular Priority Mail!

On the other hand, Priority Mail is accessible to all USPS customers; you can buy postage at the post office or even online using Click N’ Ship.

Moreover, customers who want to save but are not eligible for Cubic prices may want to consider Priority Mail Flat Rate instead.

With that, if your item can fit in one of the Flat Rate boxes and it’s less than 70 pounds, you may pay even less than Cubic customers, depending on the weight and destination.

To learn more, you can also read our posts on what is USPS Flat Rate, what is USPS redelivery, and the USPS shipping method.


Priority Mail Cubic is a special mail class offered to medium-to-high volume shippers of 50,000 parcels or more per year.

Further, the service specializes in shipping small but relatively heavy boxes and can save customers up to 89% off regular Priority Mail prices.

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Cara Suppa

Cara Suppa has been freelance writing for over a decade and holds a BA in English and an MS in Integrated Marketing Communications. Outside of work, she is an avid cook, gardener, and discount shopper.

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