---
title: "USPS Large Envelopes, Flat Mail"
url: "https://www.stamps.com/usps/large-envelopes/"
type: "page"
modified: "2025-10-09T09:50:25+00:00"
---
A Guide to USPS® Large Envelopes and Mailers: Dimensions & Pricing
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Sending a CD, magazine, legal document, or other item in a large envelope? Make sure the dimensions and prices are right before you send.

What are large envelopes?
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The term “large envelopes,” also known as flat mail, refers to First-Class Mail® sent in envelopes that exceed a certain size and are used to send items and documents you wouldn’t want folded. To send large envelopes, you need postage stamps and access to a postage meter, or you can ditch the postage meter and print postage online with us.

 [Learn About Meters](https://www.stamps.com/postage-meters/)

 ![](https://www.stamps.com/wp-content/uploads/2025/05/img-stamps-large-envelopes-light-blue-2x-1024x1024.png)

What are the dimensions of a large USPS envelope?
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Large envelopes refer to First-Class Mail sent in envelopes that exceed either 6⅛″ in height, 11½″ in width, or ¼″ in thickness. Typically, large envelopes are large enough to fit a standard, unfolded 8½″ x 11″ sheet of paper. Envelopes used for flat mail cannot be more than ¾″ thick, 12″ high, 15″ long, or weigh more than 13 ounces. USPS considers any envelope bigger than this size to be a package, so you’ll want to monitor your dimensions.

 ![](https://www.stamps.com/wp-content/uploads/2025/05/img-stamps-envelope-dimensions-bg-2x-1024x1024.png)

USPS postage rates for large envelopes
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If your large envelope exceeds USPS’ dimensions, it will be subject to higher prices. Pricing depends on the weight of the envelope with prices starting at $1.50 and increasing by $0.27\* for each additional ounce, and your large envelopes sent in the U.S. will generally arrive within three business days.

 [View Postage Rates](https://www.stamps.com/usps/current-postage-rates/)

*For First-Class mail flat, each additional ounce, 1 oz. – 4 oz., is $0.27. For 5 oz. – 9 oz., each additional ounce costs $0.28. For 10 oz. – 13 oz., each additional ounce costs $0.30.

 ![](https://www.stamps.com/wp-content/uploads/2025/05/img-stamps-padded-envelope-green-2x-1024x1024.png)

The benefits of sending large envelopes with us
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We’ll tell you exactly how much postage is required to send your mail to any domestic or international location, and you can print USPS-approved postage and address labels from the comfort of your own home or office. Send the simple way.

 [Learn More](https://www.stamps.com/usps/current-postage-rates/)

 ![](https://www.stamps.com/wp-content/uploads/2025/05/GettyImages-1298932417-1024x683.jpg)

Start mailing today
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Print your own postage in seconds without the hassle of expensive hardware or postage math. Find the plan that works for your business and start saving today.

 [ Get Started ](https://registration.stamps.com/registration/)

*For First-Class mail flat, each additional ounce, 1 oz. – 4 oz., is $0.27. For 5 oz. – 9 oz., each additional ounce costs $0.28. For 10 oz. – 13 oz., each additional ounce costs $0.30.

 ![](https://www.stamps.com/wp-content/uploads/2025/05/Stamps-Home-Mailer-11-1-1024x683.jpg)