Mailpiece Sizes

There are many different design standards for mailpieces.   A single webpage can not easily provide all specifications for every piece of mailpiece.  This webpage provides a summary of key specifications for a variety of mailpieces:

First Class Postcard-The USPS uses a different definition than many printers do for a postcard because they have a special postcard rate.  The length on a postcard is ALWAYS along the address. 

1. Not less than 3-1/2 inches high, 5 inches long, and 0.007 inch thick.
2. Not more than 4-1/4 inches high, or more than 6 inches long, or greater than 0.016 inch thick.
3. Rectangular, with four square corners and parallel opposite sides. Card-size pieces meeting the standards in 1.2.1 may have finished corners that do not exceed a radius of 0.125 inch (1/8 inch). 

So, a 4"x6" card qualifies for USPS First Class Postcard Rates but a 5"x7" card has to go at letter sized rates.

First Class, PRSRT STD or Non-Profit Letter.  The length on a postcard is ALWAYS along the address

1. Not less than 5 inches long, 3-1/2 inches high, and 0.007-inch thick.
   1. 0.007 inch thick if no more than 4-1/4 inches high and 6 inches long; or
   2. 0.009 inch thick if more than 4-1/4 inches high or 6 inches long, or both.
2. Not more than 11-1/2 inches long, or more than 6-1/8 inches high, or greater than 1/4-inch thick.
3. 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 0.125 inch (1/8 inch)
4. Within an aspect ratio (length divided by height) of 1.3 to 2.5, inclusive.

So, a 4.5"x6.5" card qualifies for USPS First Class letter Rates

First Class, PRSRT STD or Non-Profit Flat mailed at non-automation.  The length on a flat is ALWAYS the longest dimension regardless of how the address appears. 

1. Be more than 11-1/2 inches long, or more than 6-1/8 inches high, or more than 1/4 inch thick, 
2. Be not more than 15 inches long or more than 12 inches high or more than 3/4 inch thick, except for:
   1. Periodicals flats mailed under 207.26.0.
   2. Polywrapped flats, with selvage that extends beyond the contents, up to a maximum length of 15-3/4 inches. The enclosed contents must not be longer than 15 inches. Also see 4.5.3.
3. Be rectangular with four square corners or with finished corners that do not exceed a radius of 0.125 inch (1/8 inch) 

So, a 8.5"x11" card qualifies for USPS First Class Flat Rates

First Class, PRSRT STD or Non-Profit Flats mailed at presorted automation rates (you can NOT mail non-automation rates First Class Flats using these sizes).  The length on a flat is ALWAYS the longest dimension regardless of how the address appears. 

1. Minimum height is 5 inches. Maximum height is 12 inches.
2. Minimum length is 6 inches. Maximum length is 15 inches, except for polywrapped flats as allowed in 4.1.
3. For bound or folded pieces, the edge perpendicular to the bound or folded edge may not exceed 12 inches.
4. Minimum thickness is 0.009 inch. Maximum thickness is 0.75 inch.

PRSRT STD or Non-Profit EDDM.  The length on an EDDM is ALWAYS the longest dimension regardless of how the address appears. 

1. Be more than 10-1/2 inches long, or more than 6-1/8 inches high, or more than 1/4 inch thick, 
2. Be not more than 15 inches long or more than 12 inches high or more than 3/4 inch thick, except for:
   1. Periodicals flats mailed under 207.26.0.
   2. Polywrapped flats, with selvage that extends beyond the contents, up to a maximum length of 15-3/4 inches. The enclosed contents must not be longer than 15 inches. Also see 4.5.3.
3. Be rectangular with four square corners or with finished corners that do not exceed a radius of 0.125 inch (1/8 inch) 

For a more complete understanding of the rules

• Rules from the Domestic Mail Manual Click Here
• Self-paced online USPS Mailpiece Design Professional Course Click Here
• Contact the USPS National Mailpiece Design Analyst Hotline Click Here