There are many sizes of USPS boxes available. Medium Flat Rate Shipping costs less than large and you can choose from a variety of medium style boxes for your shipping needs. There are boxes that fill from both the top and the side.

This makes it easier for you to select the exact type of box that you'll require for your shipping needs. The USPS has kept their US flat rate shipping cost low to remain competitive with other vendors who also do shipping. There are three basic ways to ship your medium boxes.


Medium flat rate boxes are ideal for shipping several small or medium sized items in. They come in two styles: a top loading style and a side loading style. Each style has its own unique benefits to the sender as packaging can be made much easier when you use one style over the other depending upon the items being sent.

  • Medium flat rate boxes are 11 ¼ inches by 8 ¾ inches by 6 inches for the top loading style box.
  • Medium flat rate boxes are 14 inches by 12 inches by 3 ½ inches for the side loading style box.

These boxes are readily available online at the USPS website where you can order them to be delivered to you, or you can pick them up at your local USPS. They are free of charge as you will pay for the box when you pay for your items to be shipped. This makes it quick and easy for people to stop in at the post office and grab a few boxes for shipping.

Both boxes will cost the same amount of money as long as the contents are under 70 pounds. It's important to note that as long as the items fit into the box, the shipping cost is the same unless the items are over 70 pounds.

As restrictions will vary it's always wise to check with the USPS regarding the latest restrictions for items being mailed. It's also important to note that if you're shipping to an APO, FPO or a DPO location the restrictions are also much different than that of a regular post office box or street address. Restrictions will also change from time to time so be sure to check with the USPS before you send that package.

Flat rate boxes are a favorite of many as they are so very versatile. As long as the items fit into the box and it can be secured the items can be sent for the same flat rate regardless of how much they weight (keeping in mind that they must weigh in under 70 pounds).


Other than flat rate boxes, people can also send packages express, but since these aren’t in flat rate boxes chances are that the prices are going to be much higher.


Priority mail packages are also going to be more expensive than medium flat rate shipping costs. The flat rate boxes are designed to save people money so if you can go that route it’s usually the least expensive route to go.