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First Class Mail Shape-Based Pricing

1st class letters:

  • Must be rectangular.
  • Minimum size is 5" long x 3 1/2" high x 0.007” thick.
  • Maximum size of 11 1/2" long x 6 1/8" high x 1/4” thick.
  • Maximum weight is 3.5 oz.
  • A letter will be charged a nonmachinable surcharge if it’s a square letter 5" x 5" or larger, it doesn’t bend easily, has clasps or similar closure devices, has an address parallel to the shorter dimension of the letter, is lumpy, or the length divided by height is less than 1.3 or more than 2.5.

Postcards:

  • Must be rectangular.
  • Minimum size of 5" long x 3 1/2" high x 0.007” thick.
  • Maximum size is 6" long x 4 1/4" high x 0.016” thick.
  • Postcards over 6" long x 4 1/4" high x 0.016" thick will be charged as a letter or large envelope, depending on size

1st class Flat or large Envelope:

  • Must be rectangular.
  • Minimum size is either more than 11 1/2" long x 6 1/8" high or 1/4" thick.
  • Maximum size of 15" long x 12" high x 3/4” thick.
  • Maximum weight of 13 oz.
  • Large envelopes that exceed these dimensions will be charged package rates.

 

Priority Mail Express™, Priority Mail®, and Other Package Services:

  • Maximum size is 108" in combined length and girth (distance around the thickest part). If your item is larger, you’ll need to take it to a Post Office™ and ship with our Standard Post™ service.
  • Contents for Priority Mail Express, Priority Mail, or Media Mail® must weigh less than 70 lbs. First-Class™ packages must weigh less than 13 oz.
  • If you’re using USPS’ free Priority Mail Express and Priority Mail Flat Rate supplies, the container flaps must be able to close within the normal folds

 

Standard Post Packages:

  • Maximum size is 130" in combined length and girth (distance around the thickest part).
  • Contents must weigh less than 70 lbs

 

What would require extra postage?

  • Square envelopes
  • Envelopes that are lumpy (uneven thickness) or rigid (don’t bend easily)
  • Packages larger than 34" long, 17" wide, or 17" high
  • Envelopes with addresses written parallel to their shorter edge
  • Packages weighing more than 35 lbs
  • Books or printed material weighing more than 25 lbs
  • Tubes and rolls