The nutritional label is generally required to provide the calories in a serving of food. You can also calculate the calories in a serving from the amount of carbohydrates, fats and protein. This calculation will be an estimate because there are many factors that determine the amount of energy that you actually obtain from a food source.
Step 1
Obtain the number of grams of total carbohydrates, fat and protein in a serving of the food. This information will be on the nutritional label.
Step 2
Compute the number of calories that come from carbohydrates. Each gram of carbohydrates provides about 4 calories, so you can multiply the number of grams of total carbohydrates by 4 to get the calories that come from carbohydrates. A serving of food that has 6 g of total carbohydrates will have 4 x 6 = 24 calories from carbohydrates.
Step 3
Derive the number of calories that come from fat. Each gram of fat provides about 9 calories, so you can multiply the number of grams of fat by 9 to get the calories that come from fat. A serving that has 7 g of fat will have 9 x 7 = 63 calories from fat.
Step 4
Determine the number of calories that come from protein. Each gram of protein provides about 4 calories, so you can multiply the number of grams of protein by 4 to get the calories that come from protein. A serving that has 6 g of protein will have 4 x 8 = 32 calories from protein.
Step 5
Calculate the total number of calories that come from the serving of food by adding the calories that come from carbohydrates, fats and protein. A serving that has 24 calories from carbohydrates, 63 calories from fat and 32 calories from protein will have 24 + 63 + 32 = 119 calories.
Things You'll Need
- Nutritional label
- Calculator
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