Dimensional (DIM) weight rates apply to large, lightweight packages.Maximum combined length and girth (girth is the distance around the thickest part) is 108″.You’ll need to measure your package to make sure it meets the size standards.Use your own box and pay by weight and zone (distance): Use USPS Priority Mail Express Mailing Boxes that come in standard sizes so you don’t have to worry about measuring them.

Pay for your package based on how much it weighs and how far it’s going (the zone).

Use USPS Priority Mail Express Mailing Boxes and pay by weight and zone (distance):

When sealing a Priority Mail Express Flat Rate Envelope, the container flaps must be able to close within the normal folds.

Pay the same price for mailpieces weighing up to 70 lbs going anywhere in the U.S.

Each envelope is unique in size and structure and has differing use cases.Weight, Size, & Shape Requirements Use USPS Priority Mail Express Flat Rate Envelopes and pay one price: There are 5 different options for USPS Flat Rate Envelopes. That being said, let's dive into the different USPS Priority Mail Box and Envelope options. With a USPS Flat Rate Box or Envelope, you will be able to ship any item of any weight up to 70lbs to any location for the same price assuming it fits properly, without any bulging, within its designated box or envelope. If using non-customized boxes is not a deal breaker for you, USPS Flat Rate Shipping is a great tool to spend less on shipping. This can be a drawback for some because, unless you are a high volume shipper, you cannot get customized boxes with specific branding. In order to have access to the USPS Priority Mail Flat Rate pricing, you must use one of USPS designated Flat Rate Boxes you cannot use just any box of the same dimensions.

You can pick them up at any post office or USPS will actually ship the boxes opens in new tab open_in_new to you for free. One of the many benefits of shipping with USPS Flat Rate Boxes is that the boxes themselves are free. How You Can Use USPS Flat Rate Boxes and Envelopes to Save on Shipping

Usps flat rate box cost