Appendix B: Math for Nutrition
Surya Tewari
Nutrition Math help
This handout covers how to do basic math calculations for nutrition.
How to calculate the calories
1 Calorie= 1 kilocalorie
Example – calculating total calories from a doughnut and the number of calories from the three energy macronutrients found in a doughnut.
Doughnuts have 11g of fat, 21g for carbs and 2 grams for protein.
How to convert grams of macronutrient to calories:
1g of fat = 9 calories
1g of protein or carbohydrate = 4 calories
Calories from fat in doughnut 11x 9 = 99 calories
Calories from carbohydrates in doughnut 21 x 4= 84 calories
Calories from protein in doughnut 2x 4 = 8 calories
Total calories of a doughnut = 99+84+8 = 191 calories
Note that you can calculate grams from calories e.g. 8 calories/ 4 calories per gram = 2 grams of protein. .
Percent calories from each macronutrient
We will use the information given for a single doughnut above
% of fat in doughnut (99/191) x 100 = 51.8%
% of carbs in doughnut (84/191) x 100 = 44%
% of protein in doughnut (8/191) x 100 = 4.2%
If you know the % of a nutrient and the total calories you can calculate calories from nutrient and then grams e.g. a doughnut has 191 calories and 44 % of the calories are from fat and 4.2 % from protein. What percent of the doughnut it fat and how many calories does it represent?
100 – 44- 4.2 = 51.8% of the calories in a doughnut come from fat.
191 x (51.8/100) = 99 calories – you can then convert calories to grams.
Other resources
YouTube video on counting calories in food
Nutrition is the sum of all processes involved in how organisms obtain nutrients, metabolize them, and use them to support all of life’s processes.