Kcals measure the amount of energy provided by a food. Foods contain one or more of the following substances: carbohydrates, proteins, and fats. The amount of calories (Kcals) of a food is the sum of the kcals in each one of these categories.
Look on the food label of a product. If there is no label, look up the nutrition information on line. A good website for this is www.nutritiondata.com. See how many grams of protein the food contains. Multiply the amount of protein grams by four. This is the amount of kcals in the protein portion.
Now look at how many grams of carbohydrates included in this product. Multiply the carbohydrates by four. This is the amount of carbohydrate kcals in the food being evaluated.
Find how many total fat grams there are. Multiply this number by nine. This is the amount of fat kcals. in the food.
Add the amounts of kcals in carbohydrates, fats, and proteins together for a total kcal count.
To find the percentage of an individual component, divide the amount of kcals by the total kcal count. For example, if there are 45 kcals of fat in a 90 kcal product, you would divide 45 by 90. This food, then, is made up of fifty percent fat kcals.