USPS Box Guide

USPS shipments offer many options for box sizes depending on the Carrier Service you choose. Please click on the links below for the corresponding Carrier Service you have chosen to see more information on box sizing:

First Class Mail
First Class Mail restrictions:

  • Maximum weight is 15 oz.
  • All postcards and envelopes (or flats) must be rectangular, otherwise a non-machinable surcharge may apply.
  • Additional size restrictions apply depending on the type of mailpiece you’re sending.

Priority Mail
Priority Mail Express
Media Mail (no box sizing link available):

  • The material sent must be educational media only. This is used for sending books and other educational materials.
  • Video games, computer drives, or digital drives of any kind are not items qualified for mailing via Media Mail. 
  • Maximum weight is 70 lbs.

Related articles:

USPS Rates
Package Sizes and Dimensions: USPS International
Package Sizes and Dimensions: Measuring Packages



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