The public library of foods of the Macros app uses the manufacturer’s nutrition labels to get the nutrition facts values of each food. The calories of each food are not calculated based on the common 4:4:9 formula, where carbs and protein equal 4 calories per gram and fat equals 9 calories per gram.
Manufacturers can actually use one of six different methods in calculating calories from macros: the 4:4:9 method, 4:4:9 minus insoluble fiber, Atwater conversion factors, and three other techniques.
As an example, the USDA uses Atwater conversion factors, which is a more precise method of calculating calories from macros than the 4:4:9 formula. For more information, see http://nutribase.com/atwater.html
You can try to calculate the calories of your foods using the 4:4:9 formula by looking at their nutrition facts labels. You will notice that in most cases, the calories displayed in the nutrition facts label will not match your calculation. The same thing happens in the app, the macros you’ve logged won’t exactly match the 4:4:9 formula results.
