Mail Sizing Guide

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

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:

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."

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


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

Square or Odd Sizes

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.