Mail Sizing Guide
Letter or Self Mailer

"Letter size" encompasses oversized postcards, traditional letters, ,newsletters, and self mailers. Items are considered at letter rates if they meet the following requirements:

For more information about Folder Self Mailers, including tab information, please visit

Folded Self Mailer

According to the USPS, "A folded self-mailer is formed of at least two panels created when a single or multiple unbound sheets of paper are folded together and sealed to form a letter-size mailpiece."

The size of your piece, along with the weight, will determine what posage rate it will be eligible for:


Because of the postal equipment, anything that is a perfect square, an odd shape, OR is a rectangle, but has an aspect ratio (length divided by height) of less than 1.3 or more than 2.5 is subject to a non-machineable surcharge. In addition, because these pieces are non-machineable, they will receive a higher postage rate as the automation discounts will not apply. Because this surcharge varies depending on the size and shape of the piece, please contact Rescigno’s for more details.


Square or Odd Sizes

An item is considered a flat if it exceeds ANY of the maximum dimensions of a letter sized piece.