Why are there "missing calories" on food labels?

When you add up the calories from macronutrients (from carbs, protein and fat) and then deduct them from the total calories in the food item, there might be some marginally “missing” calories. These could come from other trace substances, such as:

• Organic acids (which on average provide 3 calories per gram).
• Polyols.
• Ethanol.
• Fermentation alcohols, which aren’t technically a macronutrient, but have calories.
• Ashes – a type of food that tends to contain a significant amount of ashes (dust) is dry cat food, which is mainly made from fish. Many manufacturers even include the term “ashes” on the label.
• Other lipids like phospholipids and neutral lipid fractions, which may not be accounted for in the three main macronutrient groups but have calories.

These marginal calories aren’t usually depicted on labels given that they’re very tiny trace amounts.

In practical terms, what you need to know is that, on average, fat provides 9 calories per gram, digestible carbohydrate 4 calories per gram, and protein 4 calories per gram too.

Then, with that knowledge, you can calculate how many fat, carbohydrate or protein calories a food item contains.

Everything else beyond that (e.g. marginal calories) is "superfluous" knowledge that doesn't have much of a practical application in nutrition, and is not needed to complete your course exercises.

AUTHOR: Alex Ruani, Research Director

Updated on: 27/10/2026