How To Count Kilojoules & Calories

Calories and kilojoules are related measures used to classify the amount of energy present in food according to Deakin University in Australia. You must first know the amount of calories in a particular food product before you can determine the quantity of kilojoules, kJ, present. Calories are the amount of heat it takes to raise the temperate of 1kg of water 1 degree Celsius and measure the potential energy in a food product. Foods are made up of carbohydrates, proteins and fats that all contribute to the amount of calories present in food.

Step 1

Read the nutritional label for the food you are going eat, and write down the number of grams of carbohydrate, protein and fat are present. For example, whole milk contains 13g carbohydrate, 8g of protein, and 8g of fat per serving.

Step 2

Multiply the number of grams of carbohydrates in the product by 4 to determine how many calories in the product comes from carbs. For example, 13g carbohydrates in whole milk * 4 = 52 calories

Step 3

Multiply the number of grams of protein in the product by 4 to determine how many calories in the product comes from protein. For example, 8g protein in whole milk * 4 = 32 calories

Step 4

Multiple the number of grams of fat in the product by 9 to determine how many calories in the product comes from fat. For example, 8g of fat in whole milk * 9 = 72 calories

Step 5

Add the calories from carbohydrates, proteins, and fats together to determine the total number of calories in the product. For example, 52 calories from carb + 32 calories from protein + 72 calories from fat = 156 total calories.

Step 6

Covert these calories to kilojoules by multiplying the total number of calories in the food by 4.184. For example, 156 calories * 4.184 = 652.704 kilojoules.

Tips and Warnings

The 4 calories per gram of carbohydrate, 9 calories per gram of fat and 4 calories per gram of protein are often referred to as the Atwater General Factors according to the book "Exercise Physiology: Energy, Nutrition, and Human Performance". Beverages containing alcohol contain 7 calories per gram of alcohol present; therefore, add them in if you desire to know the calories and kilojoules in an an alcoholic beverage.