Usually just one, but the price of it would depend on the size and weight of the letter, take it to a Post Office and they will tell you the cost.
typicaly 2 stamps
About one liberty stamp :)
75 cents.
1
only one
you need to tell us where from! If it's England or Wales then just the same as you would use to post a letter to England.
One. From USPS web site: "Forever Stamps can be used to mail a one-ounce letter regardless of when the stamps are purchased or used and no matter how prices may change in the future.
One first class stamp will carry a normal letter anywhere in the US.
It depends on the size and weight, but if it's a regular letter, a 44-cent stamp will suffice.
It takes three stamps to send a letter to Norway.
how many forever stamps = .94
One, as long as it is a 44 cent stamp.