Calories and Fat. A 1-cup serving of a typical homemade granola contains almost 600 calories and almost 30 grams of fat, of which 5 grams are saturated. The same amount of a store-bought granola is better with about 420 calories and 11 grams of fat, of which less than 1 gram is saturated. In terms of calories, granola probably isn't the best choice for your diet, especially if you're actually on a diet to lose excess weight.