Letters, envelopes, and postcard size guide for USPS

When shipping with USPS it’s imperative to always make sure you’re aware of the size of your packages. If you are unsure of the size of your mail, there are tools you can use such as ShippingEasy's measurement reference guide or the USPS guide which shows you how to measure properly.

Letter, envelope, and postcard sizes:

All the sizes listed below are the maximum sizes allowed before you are charged for the next size up. If you send a letter that’s too big it may be counted as a large envelope, and so on.

Type  Minimum Size   Maximum Size
Length Height Thickness Length Height Thickness
Postcard 5" 3-1/2"   6" 4-1/4"  
Letter  5" 3-1/2"   11-1/2" 6-1/8" 1/4" 
Large Envelope* 11-1/2" 6-1/8" 1/4" 15" 12" 3/4"

* Large Envelopes exceed one or more of the letter size maximum dimensions.

Exceeding these sizes can result in being charged much more than you expected. If you have many packages to send to many consumers it could end up hitting your wallet hard, even digging into your profits.

Using ShippingEasy's Custom Package setting allows you to save your package measurements for assured selection each time you ship. 


If you are a frequent shipper of smaller, heavier packages, ShippingEasy offers a discounted cubic pricing system called Flat Rate Green that can save you money. You can also check out USPS’s free flat rate envelopes and packages if what you ship is regularly too large.


Simplify your shipping (and save) with ShippingEasy. Start your 30-Day Free Trial.


Related articles:

What do I need to know about shipment dimensions?
What is considered to be a Regular Package for each carrier?
Package Sizes and Dimensions: USPS Domestic
Package Sizes and Dimensions: USPS International
What do I do if a package is returned due to not enough postage?

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