Food Energy (Atwater)

This formula estimates the energy a food provides by adding up the calories contributed by each macronutrient using standard Atwater factors. Proteins and carbohydrates are counted at about 4 kilocalories per gram, fat at about 9 kilocalories per gram, and alcohol at about 7 kilocalories per gram because these are typical amounts of usable energy the body can obtain from each. It is a practical approximation used in nutrition labeling and diet planning, though actual energy can vary slightly depending on the food and how it is digested.

Use this when you want to estimate the total calorie content of a meal, recipe, or packaged food from its grams of protein, carbohydrate, fat, and alcohol. It is especially useful in nutrition calculations, food labeling, and basic diet tracking.

• Forgetting to include alcohol when it is present
• Using grams of food instead of grams of each macronutrient
• Mixing up kilocalories with kilojoules or using the wrong factors