USPS Flat Rate Boxes Sizes

usps flat rate boxes sizes

The world of postage and mailing is vast, but one gem stands out for its simplicity and efficiency: the USPS flat rate boxes. Whether you’re a frequent shipper or just sending out the occasional package, understanding the different sizes of USPS flat rate boxes can make your life easier. Let’s dive deep into this offering from the United States Postal Service and explore its every facet.

What are USPS Flat Rate Boxes?

Flat rate boxes from the USPS are a type of priority mail service that allows users to ship items at a set price, regardless of the package’s weight (up to a certain limit). The most captivating aspect is their assortment of sizes, ensuring there’s a box for nearly every need.

Different Sizes and Their Specifications:

1. Small Flat Rate Box:

  • Dimensions: 8 11/16″ x 5 7/16″ x 1 3/4″
  • Ideal for small, dense items like jewelry or documents.

2. Medium Flat Rate Box:

  • Dimensions (Top Loading): 11 1/4″ x 8 3/4″ x 6″
  • Dimensions (Side Loading): 14″ x 12″ x 3 1/2″
  • Great for gifts, shoes, or smaller electronics.

3. Large Flat Rate Box:

  • Dimensions: 12 1/4″ x 12 1/4″ x 6″
  • Perfect for larger items like laptops or bulkier clothing.

4. APO/FPO/DPO Large Box:

  • Dimensions: 12 1/4″ x 12 1/4″ x 6″
  • Specifically designed for military overseas shipments.

5. Flat Rate Envelope and Padded Flat Rate Envelope:

  • Envelope Dimensions: 12 1/2″ x 9 1/2″
  • Padded Envelope Dimensions: 12 1/2″ x 9 1/2″
  • Suitable for documents, cards, or smaller items that need extra protection.

Benefits of Using USPS Flat Rate Boxes:

  • Cost Efficiency: No surprises with shipping costs. You know what you’ll pay upfront.
  • Simplicity: No need for weight measurements for packages under the weight limit.
  • Speed: They’re Priority Mail, meaning they usually arrive in 1-3 days.
  • Free Supplies: The boxes themselves are free. You only pay for postage!

Frequently Asked Questions:

How much weight can flat rate boxes hold?

Each flat rate box has a weight limit of 70 lbs for domestic shipments. For international shipments, the limit is 20 lbs for the medium and large boxes, and 4 lbs for the envelopes.

Where can I get flat rate boxes?

You can pick them up for free at any local post office or order them online through the USPS website.

Is insurance included with the flat rate service?

Yes, USPS provides insurance coverage up to $50 for Priority Mail shipments, including flat rate boxes.

Can I use my packaging for flat rate shipping?

No. To qualify for flat rate pricing, you must use the specific USPS-provided flat rate boxes.


USPS flat rate boxes present a seamless solution for shippers, combining efficiency with cost-effectiveness. By understanding the diverse range of sizes and their potential applications, you can make informed decisions that could save you both time and money. After all, in the realm of mailing, it’s not just about the destination – it’s also about the journey, and ensuring your package travels smartly.