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Preparing Shipments

Size & Weight Requirements

  1. Postcards

    Postcards must be rectangular to qualify for First-Class Mail® prices.

    Oversized postcards will be charged as a letter or large envelope.

    Size Requirements

      Minimum Maximum
    Height 3 1/2" 4 1/4"
    Length 5" 6"
    Thickness 0.007" 0.016"
  2. Envelopes

    Standard Sized Envelopes

    Envelopes must be rectangular to qualify for letter prices.


    Size Requirements

      Minimum Maximum
    Height 3 1/2" 6 1/8"
    Length 5" 11 1/2"
    Thickness 0.007" 1/4"
    Weight None N/A

    Non-Standard Sized Mail

    Non-standard mail, like square or vertical envelopes, lumpy or rigid envelopes, or mail with clasps, string, or buttons, cannot use our automated processing machines. Hand-cancelled mail is charged a non-machineable surcharge.

    Calculate Postage
  3. Large Envelopes

    Large envelopes must be rectangular to qualify for flat pricing.

    Large envelopes that exceed size requirements of a letter will be charged package prices.


    Size Requirements

      Maximum
    Height 12"
    Length 15"
    Thickness 3/4"
  4. Packages
    • Packages can be sent using Priority Mail Express®, Priority Mail®, First-Class Package Service-Retail™, USPS Retail Ground®, and Package Services.
    • Contents must not weigh more than 70 lbs. Lower weight limits may apply.
    • Girth is the distance around the thickest part of the package. In most cases, the maximum combined length and girth is 108 inches. If larger, you’ll need to take it to a Post Office™ and ship with USPS Retail Ground service.

      Measuring Package Girth
    • Dimensional (DIM) weight pricing calculates shipping costs based on the space a package takes up (a combination of length, width, and height), as well as its weight.

      How Dimensional Weight Pricing Works

Restricted & Prohibited Items

Many common household and consumer products may not be mailed through the US Postal Service®. Although these items are not dangerous when stored in your home, they can become dangerous when shaken or exposed to temperature or pressure changes.

View All Hazardous and Restricted Items

Prohibited Items

  • Air bags
  • Ammunition
  • Explosives
  • Gasoline

Addressing & Labeling

  • Print complete and correct addresses clearly in capital letters with a pen or permanent marker.
  • Do not use commas or periods.
  • Include the ZIP Code™+4 whenever possible.
  • Mark the package “Fragile” or “Perishable” when appropriate.
  • If you’re reusing a box, make sure all other addresses are covered or blacked out.
  • Affix sufficient postage to avoid charges for additional postage due or delivery delay.
View Standard USPS Abbreviations
Image of a shipping box with styrofoam pellets inside.

Packing the Box

When you mail a package, choose a sturdy box with enough room for cushioning material around the contents to protect fragile items and prevent items from shifting.

Tape your box shut and reinforce the seams with 2-inch wide packing tape. Do not use cord, string, or twine because it gets caught in the mail processing equipment.

Order Supplies

Tips for Preparing Shipments

Dropping Off Mail & Packages Expand Collapse FAQ question

If your mailpiece weighs 13 oz or less and has the correct postage, give it to your carrier or drop it off in a blue collection box or a Post Office™ lobby drop.

If your mailpiece weighs more than 13 oz and you’re using postage stamps, take it to a Post Office retail counter to mail it. If put in your mailbox for pickup service, the carrier will leave it. If dropped in a blue collection box or lobby location, it will be returned to you.