There are (amounts vary slightly according to the type of apple): 1  Approx 77 - 81 calories in 1 medium size green apple, 2¾ diameter, with peel. 2  Approx 14 calories in 1 ounce (28g) of apple without the peel. 3  Approx 15 calories in 1 ounce (28g) of apple with the peel.