How do you calculate how many stamps are needed for mailing within the United States?

Question

How do you know how many stamps are needed when weighing an envelope in grams? Thanks guys!

Answer 1

You go to the Post Office where they weigh it and tell you the amount of postage necessary.

Answer 2

A standard sized envelope with no more than about three or four sheets of regular paper in it will weigh an ounce or less -- in other words, it will need one regular first-class stamp to mail. (First class stamps are currently 42 cents).

If you're not sure whether your envelope weighs more than an ounce, you can either bring it to the post office where they'll tell you how much postage is required, or just use two stamps instead of one. The post office isn't going to care if you've got too much postage -- they only care if you don't have enough.