Question: how many forever stamps do i need for 1 oz?
Answer: A Forever Stamp is worth whatever the current rate for 1 oz of First Class mail is (currently $0.49). Each additional ounce is $0.21, up to 13 oz. Therefore a 3 oz letter requires $0.91 in postage. You can put two Forever Stamps ($0.98) and forfeit $0.08 in postage.