If you found some old postage stamps in a drawer while spring cleaning, do not throw them away. Postal stamps do not expire, so you can still use them to send mail. The value is printed on the stamp. When using old stamps, you might find it difficult to total exact postage rates; the post office will not reject the mail if you use additional postage. You can also purchase 1-cent stamps from the post office.
Determine the value of the stamp.
Weigh the envelope to determine the amount of postage needed. For first class mail, the first ounce costs 44 cents; each additional ounce costs 17 cents.
Add the value of the old postage stamps you have. For example, if you have five 4-cent Abraham Lincoln stamps and a 7-cent Benjamin Franklin stamp, you would have 27 cents' worth of stamps.
Subtract the total amount of stamps you have from the total amount you need to send the envelope. If your envelope weighs two ounces, then you need 61 cents = 44 + 17. Thus, 61 - 27 = 34. You need 34 cents to send the envelope. You can use any combination of stamps to total 34, such as two 17-cent stamps.
Adhere all of the stamps to the top right corner of the envelope. If the stamps are older, make sure that the adhesive is still effective. If not, you can glue it to the envelope.