USPS Homepage Skip navigation     USPS Home | Postal Explorer Home
Section divider line

Quick Service Guide 201

Commercial Letters and Postcards

Physical Standards for Commercial Letters and Postcards

January 2, 2011
Printer-Friendly PDF


Section divider line

Card Dimensions

inches high, 5 inches long, and 0.007 inch thick; c. Not more than 4-1/4 inches high, or more than 6 inches long, or greater than 0.016 inch thick."

5 inches
6 inches
3-1/2 inches
4-1/4 inches
0.007 inch
0.016 inch

Letter Dimensions

han 1/4-inch thick.

5 inches
11-1/2 inches
3-1/2 inches
6-1/8 inches
0.007 inch
1/4 inch

Mailpieces are classified by shape and by the way they are prepared. These classifications are based on how efficiently mailpieces can be processed on Postal Service equipment. The Postal Service classifies letters and cards into one of three categories: machinable, nonmachinable, and automation. For the purposes of determining mailability or machinabilty, the length is the dimension parallel to the address as read (601.1.4).

Machinable Letters and Cards (201.1.0)

Section divider line

If you prepare your letters and cards so that they have an accurate address and can be processed on Postal Service equipment, your mail is "machinable" and eligible for "presort" prices. Machinable mailpieces must meet specific standards, including size, shape, and weight.

Maximum weight: First-Class Mail, machinable letters and Standard Mail machinable letters: 3.3 ounces, Periodicals letters: 3.5 ounces.

Machinable letters must not meet any of the nonmachinable characteristics (201.2.0).


  • Minimum: 5 inches long, 3-1/2 inches high, and 0.007 inch thick.
  • Maximum for First-Class Mail card prices: 6 inches long, 4-1/4 inches high, and 0.016 inch thick.
  • Maximum for letters and other cards: 11-1/2 inches long, 6-1/8 inches high, and 1/4 inch thick.
  • Rectangular, with four square corners and parallel opposite sides. Letter-size, card-type mailpieces made of cardstock may have finished corners that do not exceed a radius of 1/8 inch.

Nonmachinable Letters (201.2.0)

Section divider line

Maximum weight: First-Class Mail and Periodicals nonmachinable letters 3.5 ounces; Standard Mail nonmachinable letters; less than 16 ounces.

  • Presorted First-Class Mail letters are subject to a nonmachinable surcharge if they meet any of the characteristics in 201.2.1. The nonmachinable characteristics do not apply to pieces mailed at card prices.
  • Standard Mail letters that have one or more of the nonmachinable characteristics in 201.2.1 are subject to the nonmachinable letter prices in 243.1.3 or 243.1.4

Examples of a nonmachinable letter include:

  • It has an aspect ratio (length divided by height) of less than 1.3 or more than 2.5 (a square envelope has an aspect ratio of 1, making it nonmachinable).
  • It is more than 4-1/4 inches high or more than 6 inches long and is less than 0.009 inch thick.
  • It has clasps, strings, buttons, or similar closure devices.
  • It is too rigid.
  • It has a delivery address parallel to the shorter side of the mailpiece.
  • It contains items such as pens, pencils, or keys that create an uneven thickness.
  • Letters with nonpaper surfaces, other than envelope windows or attachments that are allowed under eligibility standards by class of mail.

Automation Letters and Cards (201.3.0)

Section divider line

If your letter-size mailpiece is machinable and displays the correct delivery point barcode or Intelligent Mail barcode, you may qualify for lower, "automation" prices. A letter or card meets automation standards and qualifies for automation prices if it meets the specific addressing, barcoding, and design standards.

For additional information, see:

Maximum weight:

  • First-Class Mail automation letters: 3.5 ounces.
  • Periodicals automation letters: 3.5 ounces.
  • Standard Mail automation letters and carrier route letters: 3.5 ounces.
  • See 201.3.6 for heavy letter mail weighing over 3 ounces.

Shape: rectangular. Aspect ratio (length divided by height): 1.3 to 2.5 (201.3.4).


  • Minimum: 3-1/2 inches high, 5 inches long, and either 0.007 inch thick if not more than 4-1/4 inches high and 6 inches long; or 0.009 inch thick if more than 4-1/4 inches high or 6 inches long, or both.
  • Maximum for First-Class Mail card prices: 4-1/4 inches high, 6 inches long, and 0.016 inch thick.
  • Maximum for letters and other cards: 6-1/8 inches high, 11-1/2 inches long, and 1/4 inch thick.

Length is the dimension parallel to the address as read (601.1.3).

All letter-size reply cards and envelopes (Business Reply Mail, Courtesy Reply Mail, and meter reply mail) provided as enclosures must meet the physical standards for automation letters and cards in 201.3.17.

Quick Service Guides

Section divider line

First-Class Mail

See Quick Service Guides:

230b Nonmachinable Letters

230c Machinable Letters and Cards

230d Automation Letters and Cards

Standard Mail

See Quick Service Guides:

240a Nonmachinable Letters

240b Machinable Letters

240c Automation Letters

240d Carrier Route Letters


See Quick Service Guides:

707d Nonbarcoded Letters

707f Barcoded (Automation) Letters


Back to Top