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.