How many stamps to mail a 5ounce first class letter?

To mail a 5-ounce first-class letter in the U.S., you would typically need two Forever stamps, as each stamp covers the first ounce of a letter, and additional ounces require extra postage. As of my last knowledge update, the cost for each additional ounce is $0.24. Therefore, a 5-ounce letter would require the base rate for the first ounce plus an additional $0.96 for the extra four ounces. Always check the current postage rates for any updates or changes.