How to Convert Grams of Fat, Protein and Carbs to Calories

Read labels and do some simple math to determine how many calories from fat, protein and carbohydrates you are getting.
i Jupiterimages/Polka Dot/Getty Images

Some foods are more fattening than others because they are higher in calories. A food with a high concentration of fat has more calories than a low-fat food; that's because dietary fat contains 9 calories per gram, while protein and carbohydrates provide 4 calories per gram. So, a baked potato might have only 150 calories, but adding high-fat toppings, such as butter, sour cream and bacon bits, can more than double the number of calories.

Determine the Number of Calories

    Step 1

    Look up the nutritional breakdown of the food you are eating, paying attention to the serving size. If you are eating the amount listed as one serving, record the number of grams listed for fat, protein and carbohydrates.

    Step 2

    Multiply the number of fat grams by 9. This is how many calories from fat the food has.

    Step 3

    Multiply the number of protein grams by 4. This is how many calories are from protein. Repeat for carbohydrates, again multiplying the number of grams by 4.

    Step 4

    Add the products of fat, protein and carbohydrate grams. This is the total number of calories you are taking in when you eat that particular food.


    • The Institute of Medicine recommends that to maintain your weight, 45 to 65 percent of your daily calories should come from carbohydrates, 10 to 35 percent from protein and less than 30 percent from fat. However, if you are trying to lose weight, read labels and choose foods that provide less than 20 percent of your caloric intake from fat.

    Things You'll Need

    • Calculator or pencil and paper

    • Food labels

the nest