Because of the variance in size, it is difficult to simply say avocados have X calories and have it apply to all sizes of avocado. However, using the avocado nutrition label above we can determine that one serving of avocado equates to 1 ounce. And if you are starting with a medium sized avocado, you have a total of 5 servings or 5 ounces. Therefore half of a medium sized avocado would have approximately 2.5 servings. 2.5 servings of avocado as it states in the chart above is 130 calories.