depends on the size and weight
The amount of stamps needed for an envelope is determined by weight. Weigh your a4 envelope and you will know how much postage is needed.
The postage for a 6 x 9 envelope would depend on the weight of it.
"No, the cost of mailing a letter doesn't depend on the shape of the envelope but how much weight is actually inside the envelope. It's based on the weight."
The postage for a 6 x 9 envelope would depend on the weight of it.
The cost to mail a manila envelope will depend on the size of the envelope and the weight of the envelope. The average cost to mail a manila envelope that is 8"X11" is about $2 if the contents weigh less than one pound.
the USPS charges by weight and not by size
There is not a set price based on the size of the envelope. The final amount of postage will depend on the weight, the destination of the envelope and the thickness and/or the rigidness of the parcel.
The cost to mail a 5.75 x 8.75 envelope will depend on the weight of the envelope. As of May 2014, the cost to mail a standard letter is 49 cents.
One first class stamp (depending on weight of course).
The A4 envelope weighs about 5 grams
An empty business envelope weighs 1 gram.