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UP Tools | Postal Regulations

USPS logoAre you designing new corporate stationery? Creating a postcard? Getting ready to plan your next mailing? Don't go ANY FURTHER without reading this valuable information.

It is important to keep in mind U.S. Postal Service requirements when designing business reply mail, cards, and self-mailers. The Postal Service levies a surcharge on non-standard letter mail because it is expensive to process. Usually, it cannot be distributed on letter-sorting machines. In the facing and cancelling operation, it is often the cause of jam-ups as odd-sized letters are trapped in the machinery. With the machines operating at high speeds, such jam-ups often damage not only the non-standard envelopeUSPS Manual Icon but the mail of others.

The information contained here is intended to be used as reference material. You are strongly advised to consult your local Post Office, mailing house, or appropriate government publications. This is the only way to be sure that you are in compliance with all relevant regulations. Mohawk assumes no liability or obligation from the use of this information.

You can view the Domestic Mail Manual that is updated quarterly by the USPS.

Size/Caliper Standards for Envelopes and Business Reply Cards

The following size standards apply to all mailable matter. The thickness requirement is designed to eliminate flimsy cards and other mailpieces which do not have the stiffness to be mechanically handled.

  • All mailpieces .25 inches thick or less must be:
    1. Rectangular in shape,
    2. At least 3.25 inches high, and
    3. At least 5 inches long.
  • A mailpiece must be at least .007 (7 pt.) inches thick when it does not exceed 4.25 inches in height and 6 inches in length. Mohawk makes two text weight reply card items: Mohawk 50/10 plus and Mohawk Vellum 7 pt. Reply.
  • A mailpiece must be at least .009 (9 pt.) inches thick if it is either greater than 4.25 inches in height or greater than 6 inches in length, or both.

Address Orientation

  • Except for pieces mailed at third-class carrier-route rates, the placement (orientation) of the address on the mailpiece establishes which dimensions are its height and length. The length is the dimension that is parallel to the address as read; the height is perpendicular to the length.
  • Because of the orientation of the address, a mailpiece may not meet the minimum-size standards. All pieces that do not meet the minimum-size standards are non-mailable and prohibited from the mail.

Height-to-Length Ratios

    UP HxW ratie Grid IconThis envelope size guide shows the minimum-size mailing piece which will be accepted and the dimensions subject to a surcharge for first- or third-class pieces weighing up to one ounce. This is a convenient guide to the proper ratio of height to length. The standards call for a height-to-length ratio which falls between 1 to 1.3 and 1 to 2.5. A standard-size envelope's upper right corner will fall within the shaded area on the template. Mailing pieces which are outside these ratios will be subject to a surcharge.


  • Only light-colored envelopes and cards which do not interfere with the reading of the address and postmark should be used. Do not use brilliant colors.
  • Quality Envelopes and cards should be constructed of paper strong enough to withstand normal handling. Highly glazed paper or paper with an overall design is not satisfactory.
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