On Sunday, Jan. 26, 2014, the price to mail first class letters and postcards in the United States will increase slightly.
The cost of a first class letter (up to one ounce) will be 49 cents. The cost to mail a postcard will be 34 cents. Additionally, the cost of additional ounces for domestic first class letters will increase by 1-cent to 21 cents.
The cost of letters (up to 1 ounce) and postcards to all international addresses will increase to $1.15.
If you have "Forever" stamps, they will be good for the cost of first class postage (up to 1 ounce), no matter how much you paid for them. If you have any questions about how much postage a particular letter will need, take it to your local post office and ask them to double-check it for you.