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Physical Limitations for First Class Items

Each piece of First Class/Priority Mail is limited to the following physical qualities.


  • Maximum weight: 13 ounces
  • Items weighing more than 13 ounces should be marked Priority Mail and will receiving Priority Mail service


  • Maximum size: 108 total inches (length plus girth)
  • Minimum size: 5 inches long, 3.5 inches high, and 0.007 inches thick
  • Maximum size for postcard rate cards: 6 inches long, 4.25 inches high, and 0.0095 inches thick
Items under 1 ounce are subject to a 11-cent surcharge if they are:
  • Longer than 11.5 inches,
  • Higher than 6.125 inches,
  • Thicker than 1/4 inch, or
  • Do not feature an aspect ratio (length divided by height) between 1.3 and 2.5