Key Points:

  • USPS Priority Mail Flat Rate boxes, both large and medium-sized, are a common solution among eCommerce retailers
  • USPS Medium Flat Rate Boxes and Large Flat Rate Boxes operate on a kind of one-size-fits-most model
  • Priority Mail cubic pricing is a more efficient USPS service for shipping small packages that weigh up to 20 pounds

Experienced sellers know that shipping is an integral part of your eCommerce business — and that the associated costs can add up quickly. With your balance sheets in mind, it’s wise to seize every presented opportunity to cut down on shipping expenses, which in turn, also happens to delight customers with cost-effective delivery solutions and a custom shipping experience.

USPS Priority Mail Flat Rate boxes, both large and medium-sized, are a common solution among eCommerce retailers that allows for decreased shipping expenses regardless of the weight, size, or destination of the packages.

Although this option may be convenient, such convenience comes at a price — especially for packages weighing less than 20 pounds. A medium or large flat rate box may end up costing you up to $9.53 more than your own custom-branded box.

This article will help you figure out when you should avoid flat rate shipping, and how you can save big using your own boxes by accessing USPS Priority Mail Cubic via Easyship. Stumped? We’ve got your back. Easyship makes it so you don’t have to do the math with our free, easy-to-use shipping rate calculator.

Table of Contents

USPS Flat Rate Boxes Sizes & Weight Limitations

USPS Medium Flat Rate Boxes and Large Flat Rate Boxes operate on a kind of one-size-fits-most model. As the name suggests, this works for most, but not all. It’s not a perfect system, especially for packages of certain weights and shapes, but we’ll get into that soon.

Flat rate boxes are standard-size boxes that come in an array of sizes from extra small envelopes to the large boxes we’re discussing here. The packaging itself is provided for free and be can be picked up at the post office or ordered from USPS online.

The Medium Flat Rate Box sizes:

  • USPS Medium Flat Rate Box (top-loading): max weight: up to 70 lbs / dim: 11” x 8.75” x 6”
  • USPS Medium Flat Rate Box (side-loading): max weight: up to 70 lbs / dim: 14” x 12” x 3.5”

The USPS Large Flat Rate box size:

  • Max weight up to 70 lbs / dim 12.25” x 12.25” x 6”

How much does it cost?

Now that you know the available Flat Rate Box sizes, you may wonder how much these boxes cost. Well, these boxes are available for free at any USPS Post Office location. All you have to do to ship them is buy the corresponding flat rate postage, specifying the type of box you plan to ship when creating a shipping label.

Why USPS Medium & Large Flat Rate Boxes Might Not Be for You

These boxes offer some level of convenience to retailers, as they eliminate the need to worry about the weight, size, or shipping zone of a package. When flat rate boxes are used, standardized rates apply. Essentially, shipping costs remain the same across all the shipping zones regardless of package size and weight.

The downside is that convenience comes at a higher price, as it denies you an opportunity to ship with a cheaper USPS mail class – such as a USPS Priority Mail Cubic.

There are two major drawbacks of using medium or large USPS flat rate boxes.

  • More expensive: To ship these boxes, you have to buy the co Priority Mail postage, which can be more expensive than sending out your own box within shorter mileages via a different class of mail.
  • No custom branding: These boxes are branded with USPS materials. With that in mind, your business loses an opportunity to delight customers with custom-branded packaging that could help reinforce customer loyalty and brand name.

Should You Use Your Own Box for a Custom Size?

Using your own box for custom-size objects has two major advantages over the USPS flat rate options. Not only does it enhance your customers’ post-purchase experience, but it also cuts down shipping costs — especially for lighter packages traveling short distances.

  • Customer experience

In this day and age, where millennials have the most purchasing power in the market, most customers care about their experience with your brand and want to receive their items in nice, aesthetically-pleasing packaging.

Using your own custom-branded packaging is a savvy way to reinforce your brand and build customer loyalty through the unboxing experience, winning over more repeat customers to your eCommerce business.

When you send out packages in USPS-branded boxes that don’t tell your buyers anything about your business, you miss the opportunity to get your name out there and leave a lasting impression.

  • Cut on shipping costs

When used with the right USPS service, custom packaging is often cheaper than USPS Medium flat rate boxes. With medium and large flat rate boxes offered by the USPS for free, it’s a great, cost-cutting option.

But be warned: Even though you get these boxes for free, you may end up paying $10 more than when you use your own box and ship with a different USPS service that offers better rates.

If you want to take advantage of cost-effective USPS services, you may need to avoid flat rate boxes and use your own custom-branded packaging to cut down on your shipping expenses and improve your bottom line.

Save Big on Shipping with Priority Mail Cubic

As we mentioned above, combining your own custom packaging with the right USPS service is often more cost-effective than using flat-rate boxes. One such option is taking advantage of cubic pricing.

Priority Mail cubic pricing is a more efficient USPS service for shipping small packages that weigh up to 20 pounds. Interestingly enough, the rates offered with cubic pricing are often so deep that, even with the price of custom packaging factored in, it is still cheaper than flat rate shipping.

Simply put, cubic pricing is not only a cheaper option that saves you money but it also gives you an opportunity to reinforce your brand and build customer loyalty through custom-branded packaging.

For instance, let's say that you use your own box and it is the same size as the medium flat ate rox. This box would be 14 x 12 x 3.5 inches or even slightly bigger, say 12 x 12 x 4 inches. When you ship using pricing, your box will be in the 0.4 cubic feet pricing tier, less expensive than the flat rate box

Overall, the USPS Medium Flat rate box remains an expensive shipping option unless your package is traveling farther than 1,400 miles. In this case, taking advantage of cubic pricing to send packages in your own materials within 1,400 miles can save up to 38% in shipping costs. That adds up over time!

But how can you access and ship Priority Mail Cubic?

It is a bit tricky when it comes to shipping Priority Mail Cubic because USPS doesn’t publicize this mail class and it isn't offered to everyday consumers.

One way to access and ship with this mail class is to negotiate a direct contract with USPS that has strict guidelines to meet. You have to be able to ship a certain volume of packages per month or per year, say 40,000 packages a year.

This makes it hard for small businesses to hit such a high target, leaving big eCommerce giants to enjoy the discounts and the custom branding that comes with USPS priority Mail Cubic.

But all is not lost for small businesses that cannot meet such contractual obligations. Another way to ship Priority Mail Cubic is to access this deeply discounted service through a 3PL company that ships large volumes of packages per day.

Discover Cubic Pricing with Easyship

Fortunately, Easyship’s partners with USPS allow you to ship with cubic pricing and access even better pre-negotiated rates without entering into a strict contract. Through our platform, you have an opportunity to get the best USPS discounts and save up to 91% on shipping costs.

Plus, you get access to a suite of our shipping tools to create custom-branded packaging and delight your customers with a post-purchase unboxing experience from branded packing slips to shipping labels that bear your logo and other marketing materials.

Sign up for a free Easyship account to start supercharging your shipping!

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