Kilojoule (kJ)
The kilojoule, symbol kJ, equals 1,000 joules and is used for measuring larger quantities of energy. It was introduced to simplify calculations in nutrition, physics, and engineering, where joules alone would result in very large numbers. Kilojoules are commonly used to express the energy content of foods, fuel consumption, and industrial energy usage. The adoption of the kilojoule has standardized energy measurements across scientific disciplines and commercial applications, offering clarity and ease of use in both everyday and professional contexts.
Kilocalorie (kcal)
The kilocalorie, symbolized as kcal, equals 1,000 calories and is often referred to as a “Calorie” with a capital C in food labeling. It measures the energy in food and human metabolism, helping dieticians, nutritionists, and consumers track intake. The kilocalorie became the standard unit of energy measurement as nutrition science linked energy measurement to diet. Most scientists now use joules, but kilocalories are still commonly used in reporting food energy.