Question: how many stamps do you need for a big envelope?
Answer: A large envelope, known to the postal service as a large letter, is a maximum size of 353mm by 250mm by 25mm. The number of postage stamps required depends on the weight of the item you are sending: 0 – 100g: Two first-class or second-class stamps. 101 – 250g: Two first-class or three second-class stamps.