You've passed the point of no return on this one, since at 1 pound (16 ounces), you're mailing a package rather than a first-class letter. It makes no difference if you try to submit it properly; you'll still wind up on the same table. So, at current pricing as of 4/20/2018, 14 stamps or 50 are required, with an everlasting stamp costing $0.50. If you send 20 pounds (9 kg) or less via First Class Mail, which costs $5.95 for a standard-size envelope, then you can use the regular size stamp ($1.25). For anything over 20 pounds ($10), you have to buy a large stamp ($3.95). The post office charges based on the weight of your package. If you exceed the maximum allowed weight, you will be charged extra. The rate varies depending on how far in excess of the maximum limit you go. There is also a charge for sending packages by priority mail ($12.95-$14.95). In addition to these prices, there is a charge for each additional address on your label. This is called a "handling fee" and it's listed on your bill as "HANDLING CHARGE." For example, if you send two boxes weighing a total of 30 pounds (13.6 kg), you would pay $35.90 for postage plus handling. Two ordinary-sized letters would cost $0.70 each.