There are approximately 80 calories in a small 6-ounce apple. However, according to CalorieKing, the calorie count varies by almost 70 calories between an extra small apple and a large apple with skin.
Measure the calorie counts in apples in two different ways: by weight and by volume. When counting calories by volume, consider how the apple was prepared. Calorie counts measured by the cup vary for sliced versus quartered or chopped apples because of how much fits in the cup.
Calorie counts also vary based on the specific type of apple due both to average size and sugar content. Check online for the calorie count for specific varieties of apples, including Granny Smith, Fuji, Red Delicious, Gala and Golden Delicious.