Size and Shape of Mail Materials

The USPS pricing structure takes into consideration the cost of transportation based on size, shape and weight, and the different costs of processing mail. For example, a letter that is machinable costs less than a flat or a parcel that has to be hand-processed.

Shape is determined by width, length, thickness, and weight. Shapes that determine First-Class mail pieces are postcards, letters, large envelopes (flats), and packages (parcels). If a letter exceeds 1/4″ thickness and/or 3 1/2 ounces, it is charged as a flat. For First-Class packages, length + girth combined cannot exceed 108 inches. Length is the longest side of the parcel. Girth is the thickest point.

Non-Machinable Letters

Non-Machinable Letters with the following characteristics are subject to package (parcel) pricing:

  • Not flexible (rigid)
  • Not rectangular (squares are considered rectangles)
  • Not uniform in thickness (1/4″ variation in thickness allowed)

Examples of non-machinable letters are:

  • Rigid or odd shaped items
  • Keys, coins, pencils, pens, etc.
  • The delivery address is not parallel to the longest side of the mail piece
  • Has clasps, strings, buttons, or similar closure devices
  • Enclosed in plastic materials

A non-machinable letter weighing 3.5 ounces or less will  be charged the appropriate postage rate plus a surcharge of $0.20.

A large envelope that meets the weight and measurement criteria, but is determined to be non-machinable, will be charged as a package.