The food calorie is the primary unit of measure for food energy in the United States. It's the quantity of energy needed to heat a kilogram of water by 1 degree Celsius. You'll typically be able to find the caloric content of food from the nutritional label. You can also determine the calories in a serving of food from the amount of fats, carbohydrates and protein that it contains.
Step 1
Determine the amount of carbohydrates, dietary fiber, fat and protein in one serving of food. The nutritional label should provide this information.
Step 2
Calculate the number of calories in the food that come from pure carbohydrates. Subtract the grams of dietary fiber from the grams of total carbohydrates to get the grams of pure carbohydrates in the food. Multiply this value by 4 to obtain the calories from pure carbohydrates.
Step 3
Obtain the number of calories from dietary fiber. Multiply the grams of dietary fiber by 2 to obtain an estimate of the calories provided by dietary fiber. This value is an estimate because the calorie content of dietary fiber is highly variable.
Step 4
Compute the calories in the food that are provided by fat. Multiply the number of grams of fat by 9 to obtain the number of calories from fat in the food.
Step 5
Determine the calories in the food that are provided by protein. Multiply the number of grams of protein by 4 to obtain the number of calories from protein in the food.
Step 6
Add the calories from pure carbohydrates, dietary fiber, fat and protein. This sum is the total amount of calories in the food.
Tips and Warnings
- Carbohydrates should comprise 50 to 55 percent of your total caloric intake. Fats should provide a maximum of 30 percent of your total calories. Trans fats should provide no more than 10 percent of your total calories.
Things You'll Need
- Nutritional label
- Calculator
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