It depends mainly on the weight. Take it to the post office and they will happily calculate this for you. (I can't actually guarantee they'll be happy about it, though they certainly should be happy that someone is still using the US mail.)
1
As of June 10, one ounce of first class mail is 44¢. Every additional ounce is 20¢. So, a six ounce envelope would cost $1.44 to mail, or four forever stamps.
how many stamps for a 10.4 ounce envelope
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.
4
If you envelope weighs less than one ounce, it will take one forever stamp or one current first class stamp. If the letter and envelope weigh more than one ounce, the number of stamps will depend on the weight and the denomination of the stamps.
A 4-ounce large envelope currently costs $1.57.
2
Currently in the US up to one ounce is 45 cents. So however many stamps it takes to make that amount.
It depends on how heavy the contents are and how big the envelope is.
I successfully mail CDs all the time with 2 stamps.
It depends on the weight It depends on the weight
if it weighs an ounce or less, three stamps.