Classifications for Size, Thickness, Weight, etc. for Mail

Home Resource Center Mailing Tutorials Classifications Tutorial

Postcard:

Must mail first class to get the postcard rate. (If the organization is nonprofit, nonprofit is less expensive than postcard rates but the delivery period of nonprofit is slower)

  • Minimum size: 3 1/2 x 5
  • Maximum size: 4 1/4 x 6
  • Minimum thickness: .007
  • Maximum thickness: .016

Letter:

  • Minimum size: 3 1/2 x 5
  • Maximum size: 6 1/8 x 11 ½
  • Minimum thickness: .009
  • Maximum thickness: .25

NOTE: If mailing a letter sized stitched booklet, special requirements apply. Please inquire.

Flat:

  • Minimum size: 6 1/8 x 11 ½
  • Maximum size: 12 x 15
  • Minimum thickness: .25
  • Maximum thickness: .75

Machinable Parcel:

  • Parcels that can be processed on Postal Service Equipment
  • Minimum size: 6″ L x 3″ H x .25″ W
  • Maximum size: 34″ L x 17″ H x 17″ W
  • Minimum weight: 6oz
  • Maximum weight: 35lbs

Irregular Parcel:

Parcels that do not meet the dimensional criteria of machinable parcels including: rolls & tubes up to 26″ long & merchandise samples not individually addressed; articles that are not letter or flat size.

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