How much postage should I put on a letter?

As of July 2014, sending a standard-sized letter weighing 1 ounce or less requires one 49-cent First Class postage stamp. This is the cost of sending a letter from within the United States to a recipient who is also located in the United States.

For a letter weighing more than 1 ounce, it is necessary to add a 21-cent stamp for each additional ounce. Sending a standard-sized letter to an international recipient costs $1.15, as of July 2014. Non-standard-sized envelopes incur additional costs that vary depending on the size and shape of the envelope. Discounted postage is available when postage is purchased online.