Postage depends on the size and weight of the letter you are sending. USPS first-class mail stamps start at forty four cents for letters under two ounces.
The postage for a 6 x 9 envelope would depend on the weight of it.
The postage for a 6 x 9 envelope would depend on the weight of it.
The answer will depend on where you are posting it to!
Two stamps
One
A 6 x 9 envelope for a 1099 will cost you approximately $1.40. The exact amount will depend upon the weight of the package.
An envelope with a height exceeding 6 and one-eighths inches, and any square envelope, is non-machinable. Therefore, the rate for first class US domestic postage is $.64.
Square EnvelopesSquare envelopes are subject to the $0.20 nonmachinable surcharge.As of May 11, 2009 a regular first class stamp is $0.44 so postage for a square envelope is $0.64Technically, the 6 1/4 x 6 1/4 size classifies the letter as a "Large Envelope" (smallest dimension > 6 1/8 inches), but since it is so close (1/8" !!) they may not enforce the higher Large Envelope rate.See the post office website for more information: http://pe.usps.com/text/dmm100/postage.htm
A 6x8 inch padded envelope will require approximately $3.00 for up to 13 ounces. The USPS website offers the tools for all calculations based on weight and envelope dimensions
If it is not thicker than 1/4" and doesnt weight more than an ounce it is .44 cents.
11 1/2 inches by 6 1/8 inches
As of August 2012, first class US postage for a 6x9 3.5oz domestic letter is $1.05.