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

How to count calories

YouTube video on counting calories in food