What a Calorie Count Actually Counts

Protein and carbohydrate are conventionally counted at 4 kcal per gram, fat at 9, alcohol at 7. These are the Atwater factors, and two things about them are worth knowing. The first is that fibre is an exception: you don't fully digest it, so it yields roughly 2 kcal per gram, and that is the figure European labelling law uses. The catch is that food databases disagree about whether fibre is already inside the carbohydrate number. UK and EU labels declare carbohydrate with fibre excluded, listed on its own line underneath.

The US FoodData Central database does the opposite. Its "carbohydrate, by difference" is whatever is left after water, protein, fat, ash and alcohol, so the fibre is already in there. Count both without checking which convention you are reading and fibre gets charged 4 kcal inside the carb figure plus another 2 on top: 6 kcal per gram, for something that yields 2. Kriterion tracks which convention each source uses and only prices fibre once. The second is that 4/9/4 are averages across all foods, and their author knew it.

The same USDA handbook that established them also publishes factors specific to individual foods, because the general ones are measurably wrong for particular cases: protein in legumes, fat in nuts and carbohydrate in whole grains are all digested differently from the average. Where a database has done that work, its published calorie figure beats anything you can recompute from the macros on the label, so Kriterion trusts a source's own energy value and only falls back to calculating from macros when that value is missing or so far out that the entry looks broken.