Letters, Envelopes, and Postcard Size for USPS | Guide

When shipping with USPS it is imperative to always make sure you are 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 is too big it may be counted as a large envelope, and so on.

  • Length is the side parallel to the address
  • Height is the side that is perpendicular to the length
Type  Minimum Size   Maximum Size
Length Height Thickness Length Height Thickness
Postcard 5" 3-1/2" 0.0007" 6" 4-1/4" 1/4"
Letter  5" 3-1/2" 0.0007" 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. 

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.


Add a Comment

Please sign in to leave a comment.

  • dimensions
  • package_sizes
  • sizes
  • size
  • packagesizes
  • letters
  • unique dimensions
  • letter
  • package dimension
  • package size
  • letter stamp
  • dimensional shipping
  • answerbot_article_public