That will depend on where in the world you are and maybe the size of the envelope. Contact your local post office as they will have the most up to date prices for you.
howmuch send a letter from US to Japan
44 cents
$1.05 for simple letter
5.25
$1.05
It costs $1.05 to send a "First Class Mail International Letter"
i send postcode of uk in kohat
94 cents
i thik like a dollar
like about 346
85 cents.
$.90