There are six ways to calculate Calories for a label. Three of the most popular are:
- the 4-4-9 formula
- the 4-4-9 formula adjusted for fiber
- Atwater Factors.
Manufacturers often use 4-4-9 or 4-4-9 adjusted for fiber, and the USDA uses Atwater Factors.
4-4-9 is based on the following calculations, which are average conversion factor values:
- Protein grams x 4 = Cals from Protein
- Carbohydrate grams x 4 = Cals from Carbs
- Fat grams x 9 = Cals from Fat
Generally, we don't use 4-4-9 to calculate Calories for ESHA ingredients. (Read more how we calculate Calories in this KB article: 4-4-9: Do you use 4-4-9 to calculate calories from the grams of carbohydrate, protein and fat?)
The Atwater system is used for the calculation of the available energy of different food and is more accurate than the 4-4-9 method. Different foods contribute different caloric amounts per gram. For example, 1g of fat from one food may yield 8.4 Calories, while 1g of fat from another food may yield 9.37 Calories. For fat, the values range around 9 Calories, but not exactly 9 Calories. The same concept applies to a gram of Protein or Carbohydrate. A list of Atwater protein, carbs and fat values for a variety of foods can be found here. Generally, using Atwater Factors will result in slightly lower total Calories than using 4-4-9.
Example of Calorie calculations for Great Northern Beans using the 4-4-9 vs Atwater formulas, based on the following:
36 grams beans containing
· 22.2g Carbs
· 7.8g Protein
· 0.26g Fat
· 13.3g Fiber
Using Atwater Factors:
· 22.2g x 4.07 = 90 Cals from Carbs
· 7.8g x 3.47 = 27 Cals from Protein
· 0.26g x 8.37 = 2 Cals from Fat
· Total = 119 Cals
Using 4-4-9 formula:
· 22.2g x 4 = 89 Cals from Carbs
· 7.8g x 4 = 31 Cals from Protein
· 0.26g x 9 = 2 Cals from Fat
· Total = 122 Cals
Finally, when displaying Calories on a Nutrition Facts panel, the Calories value is rounded according to NLEA rounding rules (further skewing the discrepency).
As best practice, view your Spreadsheet report for every Recipe. The Spreadsheet details the nutrients contributed by each ingredient. When reporting values on the Spreadsheet, the program simply totals each column -- so total Calories is purely a sum of the calculated Calories from each ingredient.