USPS Homepage Skip navigation    USPS Home | Postal Explorer Home

Quick Service Guide 301
Discounted Flats
Physical Standards for Discount Flats

January 2006
Printer-Friendly PDF



Flat Dimensions

The graphic describes the minimum and maximum sizes for flats. Flat mail is: a. more than 11-1/2 inches long, or more than 6-1/8 inches high, or more than 1/4 inch thick; b. Not more than 15 inches long, or more than 12 inches high, or greater than 3/4 inch thick.

In addition to shape, the Postal Service classifies mailpieces by the way they are prepared. These classifications are based on how efficiently your mailpieces can be processed on Postal Service equipment. The Postal Service classifies discount flats as either nonautomation or automation flats.

A flat meets automation standards and qualifies for automation rates if it meets the specific addressing, barcoding, and design standards. Automation rate flats must have a delivery point barcode or a ZIP+4 barcode.


Determining Length and Height (301.1.2)

The length is the dimension parallel to the address as read; the height is the dimension perpendicular to the length. This general rule does not apply to:

  • Automation rate flats.
  • Standard Mail Enhanced Carrier Route flats.


Presorted (Nonautomation) Flats (301.2)

Shape: rectangular, unless greater than 1/4 inch thick.


  • Minimum: more than 11-1/2 inches long, or more than 6-1/8 inches high, or more than 1/4 inch thick.
  • Maximum: 15 inches long, 12 inches high, and 3/4 inch thick.
  • Maximum size for Enhanced Carrier Route flats: 14 inches long, 11-3/4 inches high, and 3/4 inch thick.

Maximum weight:

  • First-Class Mail: 13 ounces.
  • Standard Mail: less than 16 ounces.
  • Bound Printed Matter: 15 pounds.


Nonmachinable Surcharge (301.2.1.2)

First-Class Mail nonautomation and automation flat-size pieces that weigh 1 ounce or less are subject to the $0.058 nonmachinable surcharge if any one of the following applies:

  • The piece is greater than 1/4-inch thick.
  • The length is more than 11-1/2 inches or the height is more than 6-1/8 inches.
  • The aspect ratio (length divided by height) is less than 1.3 or more than 2.5.

The nonmachinable surcharge does not apply to Standard Mail flats.


Automation Flats (301.3)

Flats may qualify for the automation discount based on the dimensions and characteristics for the automated flat sorting machine (AFSM) 100 in 301.3.3 or upgraded flat sorting machine (UFSM) 1000 in 301.3.4. See Quick Service Guide 301a, Designing Flats for Automated Processing, for an overview.

For the specific DMM standards applicable to this category of mail, consult the DMM sections referenced above and the general sections within each DMM module.


Quick Service Guides

First-Class Mail
See Quick Service Guides:
330a Presorted Flats
330b Automation Flats

Standard Mail
See Quick Service Guides:
340a Presorted Flats
340b Automation Flats
340c Enhanced Carrier Route Flats

Bound Printed Matter
See Quick Service Guide:
360 Presorted Flats

Media Mail
See Quick Service Guide:
370 Presorted Flats

Library Mail
See Quick Service Guide:
380 Presorted Flats

See Quick Service Guides:
707e Nonautomation Flats
707g Automation Flats


Back to Top