3 1/2" x 5"
The postage is $1.76 for a standard letter envelope of 2 oz.
Since the envelope is 5.25 X 5.25 inches square, the postage is .70 cents for first class. This rate is for an envelope that weighs .5 ounces. The postage may be higher depending on the weight of the envelope.
The postage is standard first class 1 ounce (a "Forever" stamp).
For a first class envelope is cost 44 cents
One first class stamp (depending on weight of course).
no, one first class stamp is all that is needed
First class postage for a regular envelope weighing less than one ounce from the U.S. to Greece is $1.20 in March, 2016.
Used currently (2010) for First Class standard envelope domestic postage for a letter weighing from 1 to 2 ounces.
Legally - no. You're expected to pay postage if you re-use it.
Postage is .45 for a letter 1oz. or less and a large envelope weighing 1oz. or less is .90
The same as a standard A4 envelope ... 44 cents. There is only a price break for postcards. If it's any kind of envelope, that can be sealed, it requires first class postage.
You will need postage for the weight of the envelope (probably 2 ounces, for 4 sheets of paper in a 10x13 envelope), plus a surcharge for the size of the envelope. Best guess: $1.19 for first class mail within the United States, as of Feb. 2014.