The following calculations/information about calories in juicing is from the LiveStrong website... I think it's a pretty accurate account... Hope this helps!
"When you make fresh juice at home, you need to keep an eye on how many calories you are consuming. Juicing often uses the whole fruit, which includes the skin, seeds and core. Typically, most people do not eat the core when eating fresh fruits, and some discard the skin, too. The calories in the core and skin of a piece of fruit can significantly affect your calorie count. Natalie Savona, author of "The Big Book of Juices and Smoothies," suggests an apple's core accounts for about 10 percent of total calories, while the skin accounts for about 13 percent.
List the recipe ingredients you are using, which might be different than those called for by your recipe. For instance, if your recipe calls for two small apples, and you are using two medium-size apples, the calorie count will be higher than that of the recipe.
Find the calories listed for the correct-size fruit you are using. For example, the U.S. Department of Agriculture provides the following for a raw apple, which includes the skin and core: A large-size apple weighing 223 grams has about 191 calories; a medium-size apple weighing 182 grams contains about 156 calories; and a small apple weighing 149 grams has about 149 calories.
Use a calculator and add these calories up to find your total juicing calories.
Deduct 10 percent of the calories of a raw fruit if you discard the core and 13 percent if you discard the skin. It is more common to remove the core before juicing than the skin, but personal taste preferences differ."