How many stamps needed for a 1.4 ounce letter?

To send a 1.4-ounce letter in the United States, you typically need two first-class stamps. The standard first-class stamp covers up to 1 ounce, and for each additional ounce, you usually need to add an extra ounce stamp. Therefore, for a letter weighing 1.4 ounces, you'll need one first-class stamp plus an additional ounce stamp.