Explaining different shipping and package sizes

UPDATED: January 10, 2018

For current USPS® information, refer to Mailing Standards - Domestic Mail Manual.

The USPS site contains the current physical standards and sizes for letters, parcels, and flats.

USPS Postage Price Calculator is a free online tool that allows you:

  • Calculate Postcard price
  • View Flat Rate Envelopes
  • View Flat Rate Boxes
  • Calculate price based on Shape and Size

Another helpful resource: Guide to Shipping - interactive guide with the latest prices, news and updates, and ways to save.