We help alot of clients not only design custom postcards and similar pieces of media, but also help them foresee what particular costs of mailing them are.  You wouldn’t want a design to be too big, causing the size of the envelope to be classed in the higher price group.  The following has been referenced from the USPS Website.

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.

 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.
  • Can’t include any hazardous materials.

Large Envelopes

  • Maximum size of 15″ long x 12″ high x 3/4” thick. Large envelopes that exceed these dimensions will be charged package rates.
  • Maximum weight of 13 oz.
  • Most hazardous materials cannot be shipped.

Packages

  • Maximum weight of 13 oz.
  • Most hazardous materials cannot be shipped.
  • With few exceptions, cigarettes and smokeless tobacco shipments cannot be mailed.