wikiHow Calculate Calories from Protein Calculator To calculate calories from protein, you can use the following formula: 1 gram of protein = 4 calories For example, if a food item contains 20 grams of protein, you can calculate the calories from protein as follows: 20 grams of protein x 4 calories per gram of protein = 80 calories from protein Therefore, the food item contains 80 calories from protein. It's important to note that while protein is an important macronutrient that provides energy and supports muscle growth and repair, it's not the only nutrient that contributes to the total calorie count of a food item. The calorie content of a food also depends on the amount of fat, carbohydrates, and other nutrients present. Page