Question: how many stamps do i need for a 6.5 x 9.5 envelope?
Answer: A 6” x 9” envelope weighing up to 1 ounce requires one $. 50 first class rate stamp. For each additional ounce, you'll have to pay $0.21. So, for weight between 1 and 2 ounces, it'll cost you $0.71.