how many stamps does it take to send a plain envelope from the U.S. to Canada?

Answer 1

I'm not sure what you mean by plain envelope. However, postage is based on weight. If you mean a business size envelope with 1-3 sheets of paper in it....its probably going to be one ounce or less...therefore the postage will be 39 cents. There is no extra charge for cross border mail. If you want to send it airmail, or express mail that will cost extra.