Calculating Percent kcal from Macronutrients
What is a percentage?
In mathematics, a percentage is a number or ratio that represents a fraction of 100 or 1. Percentages
are often expressed by utilizing the symbol % or sometimes expressed as a decimal. For example, 35% is
equal to the 0.35 expression. When the % symbol is utilized, it is representing a fraction from 100;
however, when the decimal version is used, it represents a fraction of 1. It is important to remember
that when dealing with percentages, it will always be part of a whole and never bigger than the whole.
For example, you can never have a % that is greater than 100. Why is that? If you only had one pie, this
pie will represent our 100% or a whole. How could it be possible to eat 110% of that pie, when there is
only one whole pie?
Now let’s move on to calculating the percent of kcal that comes from each macronutrient. To calculate
the percentage of energy derived from each nutrient requires the following equation:
kcal from individual macronutrient x 100 = % of energy from that macronutrient
Total kcal
In order to use that equation, we have to first calculate the kcal from each macronutrient. To determine
this, you must first remember that every gram of carbohydrate yields 4 kcal of energy (4 kcal/g), every
gram of protein yields 4 kcal of energy (4 kcal/g), and every gram of lipid yields 9 kcal of energy (9
kcal/g). While alcohol is not considered a nutrient, it does yield energy. Every gram of alcohol yields 7
kcal of energy (7 kcal/g). To perform your calculations, you begin with the number of grams for each
macronutrient (and alcohol if present). For example, if we looked at the nutrition facts panel on a 12
ounce can of regular beer, we would find the following information:
Carbs = 13.2 g Lipids = 0.0 g Proteins = 1.2 g Alcohol = 12 g
With these values, you can then calculate the total kcal value for each as shown below.
13.2 g of Carbs x 4 kcal/g = 52.8 kcal of energy from carbs in this can of beer
0.0 g of Lipids x 9 kcal/g = 0 kcal of energy from lipids
1.2 g of Proteins x 4 kcal/g = 4.8 kcal of energy from proteins
12 g of Alcohol x 7 kcal/g = 84 kcal of energy from alcohol
Next, add all kcal values from each macronutrient and alcohol together to determine the total kcal.
52.8 kcal from Carbs + 0 kcal from Lipids + 4.8 kcal from Proteins + 84 kcal from Alcohol = 141.6 Total
kcal of energy in this can of beer
Now that we know how to convert grams into kcal and calculate total kcal, we can now move on to
calculating percent of kcal from macronutrients. Continuing with our beer example from above, we are
going to use the following equation:
kcal from individual macronutrient x 100 = % of energy from that macronutrient
Total kcal
