Which one of the "big 3" macronutrients is the most calorically dense at 9 calories per gram?

Fat is by far the most calorie loaded of the macronutrients, containing 9 calories per gram compared to only 4 calories per gram for proteins and carbohydrates. Although a low fat diet is generally desirable for persons who would like to restrict their caloric intake, a no fat diet is no recommended by nutritionists or doctors since there is a dietary need for some fat in the diet.

This is giving me a headache i have asked others and they don’t know it either