A first-class envelope in the United States can measure up to 11.5 inches in length, 6.125 inches in height, and 0.25 inches in thickness. It must weigh no more than 1 ounce for the standard rate, with additional weight resulting in higher postage costs. The envelope should also be rectangular in shape to qualify for first-class rates.
28p
First class mail is delivered in 3 to 5 days
First class is letter weighing less than 13 ounces in a standard envelope.
3 1/2" x 5"
One first class stamp (depending on weight of course).
For a first class envelope is cost 44 cents
no, one first class stamp is all that is needed
If its US domestic and a standard letter it costs 59 cents First Class. If the item is rigid or in an odd sized envelope it costs 79 cents First Class. You can calculate your postage at http://postcalc.usps.gov/.
As of August 3, 2010, the rate to mail a square envelope in the United States, domestic first class mail, was 64 cents.
One 'first class' stamp will get an ordinary business envelope from any address in Canada to any other address in Canada.
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 cost will depend upon the size and also the weight of the envelope. Also if it is first class or second class mail, and the country you live in. If you are in UK you can go to Royal Mail website and get the exact price of the cost but you need the weight of the envelope.