Being Square

The question: what is the US postage on a square envelope?

From the ever-clear US Post Office site:

1.2 Nonmachinable Criteria

A letter-size piece is nonmachinable if it has one or more of the following characteristics (see 601.1.1.2 to determine the length, height, top, and bottom of a mailpiece):

a. Has an aspect ratio (length divided by height) of less than 1.3 or more than 2.5.

b. Is polybagged, polywrapped, enclosed in any plastic material, or has an exterior surface made of a material that is not paper. Windows in envelopes made of paper do not make mailpieces nonmachinable. Attachments allowable under applicable eligibility standards do not make mailpieces nonmachinable.

c. Has clasps, strings, buttons, or similar closure devices.

d. Contains items such as pens, pencils, keys, or coins that cause the thickness of the mailpiece to be uneven; or loose keys or coins or similar objects not affixed to the contents within the mailpiece. Loose items may cause a letter to be nonmailable when mailed in paper envelopes; (see 601.3.3).

e. Is too rigid (does not bend easily when subjected to a transport belt tension of 40 pounds around an 11-inch diameter turn).

f. For pieces more than 4-1/4 inches high or 6 inches long, the thickness is less than 0.009 inch.

g. Has a delivery address parallel to the shorter dimension of the mailpiece.

h. Is a self-mailer that is not prepared according to 201.3.14.

i. Is a booklet that is not prepared according to 201.3.16.

 

Oh sure, that's intuitively obvious.