Question: how to calculate the percentage of calories from carbohydrates?
Answer: Nutrient percentages are the percentage of the day's calories coming from each macronutrient. ...  Carbohydrate calories = Carbs (g) * 4.0. Protein calories = Protein (g) * 4.0. Fat calories = Fat (g) * 9.0. In the example above, the fat calories per gram are higher than protein and carbohydrates.