USPS Small Flat Rate Boxes measure 8.625 by 5.375 x 1.625”. Then you start getting into the box sizes. These envelopes have a bit of extra space inside of them and work great for books. Padded Flat Rate Envelopes are even larger still, measuring 12.5” x 9.5”.

It’s intended (no surprise here) for use with legal documents that need to be shipped quickly yet cost-effectively. The Legal Flat Rate Envelope is slightly larger, measuring in at 9.5” x 15”. This envelope is really designed only for sending small documents, pamphlets, and other things that can slide inside of this envelope. The Flat Rate Envelope is the smallest, measuring in at 12.5” x 9.5”.

There are a couple of different flat rate box sizes available from the USPS, with the “large” flat rate box size being the biggest of the bunch (as of 2022, anyway). Just How Big is the USPS Large Flat Rate Box Size?

… And that’s just the tip of the iceberg!

How much you can expect to spend on USPS large flat rate boxes.

The benefits of using the USPS Flat Rate Shipping option.

Just how big the USPS large flat rate box size is.

It’s almost impossible to overstate the popularity of the USPS Flat Rate Shipping option. From the moment that the USPS offered Flat Rate Shipping it was a huge success, especially when they rolled out the USPS large flat rate box size. This service provided USPS customers with an opportunity to ship pretty much anything and everything (so long as it fit inside of the USPS large flat rate box) at deeply discounted prices compared to traditional rates. That was, and continues to be, a game changer!īelow we highlight (almost) everything you need to know about taking advantage of the USPS large flat rate box size, too. We go over things like:

Usps flat rate envelope sizes