Battery Equivalents and Replacements

kcal to kJ: Kilocalories (kcal) to Kilojoules (kJ) Converter

Kilocalories (kcal) and kilojoules (kJ) are units of energy, and their conversions are simple and straightforward - one just has to remember that "k" stands for "kilo," which is, according to the SI prefixes table, 103 (one thousand) of the main value.

The kilocalorie, as a unit of energy, is tied to the energy required to increase or decrease the temperature of water.

Published: January 27, 2024.

To convert kilocalories to kilojoules, write the value in kilocalories and click 'Calculate':

Kilocalories (kcal) to Kilojoules (kJ)

Kilocalories (kcal):

Kilojoules (kJ):

To convert kilojoules to kilocalories, check our kJ to kcal: Kilojoules (kJ) to Kilocalories (kcal) Conversion article.

How To Convert Kilocalories (kcal) to Kilojoules (kJ)

The relationship between small calories and joules, or kilocalories and kilojoules, is as follows:

1 cal = 4.184 J

1 J = 1/4.184 cal = ~0.239 J


1 kcal = 4.184 kJ

1 kJ = 1/4.184 kcal = ~0.239 kJ


Kilocalories (kcal) to Kilojoules (kJ) Conversion Table

The following chart contains the most common Kilojoules (kJ) values converted to kilocalories (kcal):

Kilocalories (kcal) Kilojoules (kJ)
1 4.184
10 41.84
50 209.2
100 418.4
500 2092
1000 4184
2000 8368
3000 12552
5000 20920
10000 41840
100000 418400


If You wish to convert values that are not in the table, please use the kilocalories to kilojoules conversion calculator.

A Closer Look at Calories: The Energy Measurement in Nutrition

Calories are a widely recognized unit of measurement for energy, particularly in the context of food and nutrition. The term "calorie" has its roots in the 19th century and has evolved to become a key element in dietary planning and understanding food energy.

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The Origin of the Calorie Concept

The concept of the calorie emerged in the early 19th century, primarily through the work of French chemist Nicolas Clément. Initially, calories were used in the field of physics and chemistry to measure heat.

Clément's calorie was defined as the amount of heat required to raise the temperature of one kilogram of water by one degree Celsius.

This early definition set the stage for the calorie's later adoption into the world of nutrition.

Transition to Nutritional Contexts

By the late 19th and early 20th centuries, the calorie had been adapted to measure the energy content of food. This transition was largely driven by the work of scientists like Wilbur Olin Atwater, an American chemist who studied human nutrition and metabolism.

Atwater's experiments led to the development of a system to measure the energy provided by proteins, fats, and carbohydrates in terms of calories.

Small Calorie vs. Large Calorie

In the realm of science, the calorie (small 'c') is defined as the amount of energy needed to raise the temperature of one gram of water by one degree Celsius.

However, in nutrition, the term "calorie" usually refers to the kilocalorie (1,000 small calories), denoted as Calorie with a capital 'C'. This larger unit is used to express the energy content of foods. For example, when a food label indicates 200 Calories, it is actually referring to 200,000 small calories or 200 kilocalories.

Calories in Modern Nutrition

Today, calories are a fundamental part of nutritional science and dietetics. They are used to quantify the energy that food provides to the body.

This measurement is crucial for understanding dietary needs, managing weight, and studying the relationships between diet, health, and disease.

Comparison with Joules

While calories are the preferred unit in nutrition, joules are the standard unit of energy in the International System of Units (SI). One small calorie is equivalent to approximately 4.184 joules.

The use of joules is more common in scientific and technical fields outside of nutrition. Despite this, the concept of calories remains deeply ingrained in everyday language and dietary discussions.

Note: the most commonly used calorie, "thermochemical calorie", equals exactly 4.184 joules.

The calorie, with its historical roots in physics and chemistry, has become an integral part of understanding and measuring the energy in food. Its adaptation and use in nutrition have helped shape modern dietary guidelines and public health policies.

While the joule serves as the universal unit of energy in most scientific contexts, the calorie continues to hold a specific and significant place in the world of nutrition and dietetics.