How to Calculate the Total Calories in Food
- 1). Calculate the calories using the nutrition label, if the food has one. Though most labels contain the total calories contained in the product, you can also calculate the total calories by looking at the amount of fat, carbohydrates, and protein. A gram of fat contains 9 calories, whereas 1 g of protein or carbohydrate contains 4 calories. For example, a food with 15 g of carbohydrates, 10 g of protein and 5 g of fat would contain (15 x 4) + (10 x 4) + (5 x 9) calories, for a total of 145 calories. Your calculations may differ slightly due to rounding of the grams of fat, carbohydrate, and protein content on the label.
- 2). Look for the nutrition information on an online food database, such as CalorieKing, if the food that you want to eat is not from a package. These websites are databases of hundreds of foods and their nutritional information. By searching by type of food, for example, apple, or brand of food, like a particular fast food chain, you will be able to obtain the same information that you could from the nutrition label.
- 3). Calculate calories based on the portion size of the food you are eating. Calorie content in food is determined based on portion size, and often pre-packaged foods contain more than one serving per package. If possible, use a food scale to weigh out the portion size for the most accurate assessment. If this is not possible, use your best estimate by counting out nuts, crackers, or chips, for example. If you ate more than one serving, multiply the calories per serving by the number of servings you are eating to come up with an accurate amount of calories eaten.