Take your envelope to the Post Office and they will weight it, and give you your answer as the cost of mailing anything is done by weight.
$1.92 for plain first class mail within the United States
That weight makes it a large envelope, which costs $1.86. Four stamps would cover it, though that would overpay by ten cents.
$1.92
The first ounce will cost 44 cents. Each additional ounce, or fraction, is another 17 ounces. That would be 78 cents for that envelope at the start of 2011.
A 4-ounce large envelope currently costs $1.57.
I think you mean 9x12 envelope.
That depends on where you are sending it from (you country of origin) and to (the country of destination).
how many stamps for a 10.4 ounce envelope
how many stamps for a 3.4oz envelope
As of 2016, a 2.5 ounce envelope it would cost 93 cents (one Forever stamp plus two extra ounces).
Postage is determined by weight and by size. An envelope with three pieces of normal paper can normally be sent with one first class postage stamp. Additional stamps may be required based on additional ounces and on the size of the envelope.
After 3.5 ounces, the item moves up to large envelope rates. The current rate as of 2016 for an 11 ounce large envelope is $3.18.
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 number of stamps needed for an envelope depends on the weight and destination. The weight limit for a standard USPS First-Class Mail envelope is 3.5 ounces. For an envelope weighing 12 lbs, you would need to use a different shipping method, such as USPS Priority Mail or USPS Priority Mail Express. The specific number of stamps required can be calculated using the USPS postage rate calculator or by visiting your local post office.
The first ounce or less: 44 centsMore than one ounce but not over 2 ounces: 61 centsMore than two ounces but not over 3 ounces: 78 centsMore than three ounces but not over 3.5 ounces: 95 centsIf over 3.5 ounces, the letter is subject to the large envelope rate.As you letter weighs 4 ounces, but less than 5 ounces, it is subject to the large envelope rate. The large envelop rate for four ounces is $1.39. Which means you will need to use 4 forever stamps (44 cent stamps).