How do you calculate energy percentage from foods?

For my nutrition class I had to keep a journal all day of the food I have eaten and total up all of the carbohydrates, proteins, calories and fats. Then I have to figure out the percentage of energy from each group. Is there a formula for doing this?How do you calculate energy percentage from foods?
If you know the amounts of fats, proteins, and carbohydrates, then your total caloric intake should be 4(grams carb)+ 4(grams protein)+9(grams fat) %26lt;-- that many calories TOTAL. The percentage carb and protein is then their respective quantity in calories (ie, four times the amount of grams of each) divided by the total calories, and multiplied by one hundred. For fats, you use the quantity in calories, in this case 9 times the grams of fat, then again divide by the total calories consumed and multiply by one hundred.



Example: 5 grams fat, 4 grams carbs, 3 grams protein. Total calories= 4(4)+4(3)+9(5)=16+12+45= 73 Total Calories.

Percent carb= 4 calories per gram(4 grams carbohydrate)/73 calories total *100=100(16/73)= 21.9

Protein: 100(4(3)/73)=16.4

Fat:100(9(5)/73)=61.6...

Double check by adding the percentages : 21.9+16.4+61.6=99.9... close enough to 100