Can You Use Any Box To Ship USPS? (Priority, First Class, Internationally + More)

One of the marks of adulthood is keeping a box because it’s a “good box,” and this practice comes in handy when it comes time to ship something.

The United States Postal Service carries plenty of flat-rate box options, and they will even ship them to you for free if you order them online.

But you might be wondering: Can you use any box to ship USPS? Are you locked into the USPS Flat Rate service? I have the answer you seek.

Can You Use Any Box To Ship USPS?

While the United States Postal Service does encourage the use of their Flat Rate shipping boxes, customers can send packages using pretty much any box they desire. There are a few limitations in terms of size and appearance, but most boxes, if prepared correctly, are eligible for USPS shipping.

For more details on using or reusing a box properly to ship USPS, which services require a USPS box specifically, and some shipping best practices, keep reading below!

How Do You Use Or Reuse a Box To Ship USPS?

The site has a lot of advice for how to use or reuse a box of your own for shipping through their system.

To start off, there are five things you’ll want to consider when choosing your own box:

  • Is it plain, or does it have logos/labels that need to be covered/removed?
  • Does it advertise any of the items that are prohibited by USPS from being mailed? This includes firearms, alcohol, toxic materials, etc.

According to the USPS website, if a box contains any words or pictures referencing these items, the package will be taken out of circulation.

  • Is the box a standard size? Boxes in irregular sizes/shapes won’t go through the scanning/sorting/processing machines and may be subject to extra fees.
  • Is the box sturdy enough? USPS doesn’t make a habit of abusing packages, but boxes do need to stand up to a certain degree of handling and jostling.
  • Is the box small enough? While the Postal Service’s limits on box sizes are by no means small, customers must nonetheless ensure their packages do not exceed 108 inches in total length and girth.

For more information on preparing your box for shipment, check out the USPS page here.

Is It Cheaper To Use Your Own Box To Ship With USPS?

When it comes to using your own box versus a USPS Flat Rate box to save money, it really depends on the dimensions and weight of your package, as well as the destination.

For example, points out that if you’re sending something lighter, regular Priority Mail can actually be cheaper than Priority Mail Flat Rate prices.

So if you want to determine which service is cheapest, you are going to have to do the legwork to compare and contrast.

You can do this easily with the postage calculator tool; enter the shipment information, and you will receive all the shipping possibilities with estimated prices.

Can You Use Any Box To Ship USPS Priority Mail?

Can You Use Any Box To Ship USPS Priority Mail?

As long as you are not attempting to access the USPS Priority Mail Flat Rate shipping prices, you can use any box to ship Priority Mail.

If you want to pay Priority Flat Rate prices, however, you will need to use a Flat Rate box. That said, they are totally free at Post Office locations or online.

(In case you were wondering about Priority Mail Express, this service does not ship boxes – only letters and envelopes.

If you want to send a box domestically overnight or within two days, you will have to choose a different shipper, like FedEx or UPS.)

Can You Use Any Box To Ship USPS First Class?

You can use any box to ship USPS First Class, provided your item meets the 15.999-ounce weight limit.

First Class package shipping is really only for small, light boxes – if you want to send something heavier/bigger, you’ll have to choose a different shipping service.

That said, USPS doesn’t sell any boxes specifically for First Class, so this is the one shipping service where you are expected to provide your own.

Can You Use Any Box To Ship Internationally With USPS?

If you do not want to ship using any of the USPS Priority Mail International Flat Rate boxes, you can certainly use your own box to ship internationally.

You can send parcels internationally using Global Express Guaranteed, Priority Mail Express International, Priority Mail International, and First-Class Package International.

However, you will want to ensure that the box you intend to use for any of these services meets all the requirements for international mail shipping.

What Is the Smallest Box You Can Ship USPS?

At, the site reports that the smallest package USPS will accept is six inches by three inches by ¼ of an inch or 6” x 3” x .25”.

The site also has a helpful recommendation if the box you have chosen is smaller than that.

Their advice? Go ahead and enter the minimum box dimensions (if you are purchasing postage online), print it out, and affix it.

Very rarely does USPS, in their opinion, remove a box for being too small.

What Is the Largest Box You Can Ship USPS?

Each mail class is different in terms of maximum box size with USPS, but cites the two most popular classes and their max box sizes:

  • First-Class Package: Maxes out at 22”x18”x15”
  • Priority Mail: Total size (Length x Girth) cannot exceed 108 inches

For the other classes, the maximum size is the same as Priority Mail, with the one exception of USPS Retail Ground, which is 130 inches in total.

To learn more, you can also read our posts on whether or not USPS notarizes documents, if USPS scans packages, and also if USPS delivers to the door.

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Marques Thomas

Marques Thomas graduated with a MBA in 2011. Since then, Marques has worked in the retail and consumer service industry as a manager, advisor, and marketer. Marques is also the head writer and founder of

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