Battery Equivalents and Replacements

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

Kilojoules and kilocalories 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 and that calorie is tied to the energy required to increase or decrease the temperature of water.

Published: January 27, 2024.

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

Kilojoules (kJ) to Kilocalories (kcal)

Kilojoules (kJ):

Kilocalories (kcal):

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

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

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


Kilojoules (kJ) to Kilocalories (kcal) Conversion Table

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

Kilojoules (kJ) Kilocalories (kcal)
0.5 0.1195
1 0.2390
5 1.1950
10 2.3901
50 11.950
80 19.120
100 23.901
500 119.50
1000 239.01
10000 2390.1


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

What is a Calorie?

Calories are a unit of measurement used to quantify the amount of energy provided by food and beverages. In scientific terms, a calorie is defined as the amount of heat required to raise the temperature of one gram of water by one degree Celsius.

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This unit, however, has two distinct scales commonly used: the small calorie (cal) and the large calorie (Calorie) or kilocalorie (kcal).

The small calorie, often referred to simply as a calorie (with a lowercase 'c'), is a unit of energy that is used in physics and chemistry. It’s based on the specific heat capacity of water and is primarily used in scientific contexts. This calorie is defined as the amount of energy needed to raise the temperature of one gram of water by one degree Celsius at a pressure of one atmosphere.

On the other hand, the term "calorie" in the context of food and nutrition refers to the large calorie (Calorie), also known as the kilocalorie (kcal). This is equivalent to 1,000 small calories. When food labels mention "calories," they are actually referring to kilocalories. For example, a food item that contains 200 calories actually contains 200,000 small calories or 200 kilocalories of energy.

The distinction between these two units, although subtle, is significant. In nutritional contexts, using the term "calorie" to mean "kilocalorie" is a simplification for consumer convenience. This has been a common practice since the early 20th century, when food energy started to be measured in terms of calories.

It is crucial for individuals studying nutrition, dietetics, or food science to understand this distinction, as it affects the calculation and understanding of energy intake and expenditure.

Brief History of Joule

The joule, named after the English physicist James Prescott Joule, is a unit of energy in the International System of Units (SI). Its history is intertwined with the development of the concepts of energy and work in the field of physics during the 19th century.

Emergence of the Concept

The foundation for the joule as a unit of energy was laid by the work of James Prescott Joule in the mid-1800s. Joule, an avid experimenter and a key figure in the field of thermodynamics, is most famous for his experiments that demonstrated the interconvertibility of heat and mechanical work.

This led to the formulation of the first law of thermodynamics. Joule's experiments involved measuring the temperature changes in water when it was stirred mechanically, showing that work done could be converted into heat.

Standardization of the Unit

In honor of his groundbreaking work, the unit of energy in the SI system was named the "joule" in 1889 during the first International Congress of Electricians.

A joule is defined as the energy transferred when a force of one newton is applied over a distance of one meter. In other words, it is the energy expended in applying a one-newton force over a one-meter distance.

Joule and the Modern Understanding of Energy

The establishment of the joule as a standard unit of energy marked a significant step in the scientific understanding and measurement of energy. It provided a universal and consistent way to quantify energy in various forms, whether it be electrical, mechanical, thermal, or kinetic.

Comparison with Calories

While the joule is the standard unit of energy in the SI system, the calorie remains in use, particularly in the field of nutrition. A calorie is defined as the amount of heat needed to raise the temperature of one gram of water by one degree Celsius.

Distinct Origins and Applications

The joule and the calorie have different origins. The joule emerged from the study of mechanics and thermodynamics in the 19th century, while the calorie has its roots in earlier 19th-century work in heat and thermometry.

Joules are widely used in physics, engineering, and many scientific disciplines, whereas calories are predominantly used in nutrition and everyday discussions about food energy.

Conversion and Equivalence

One of the key relationships between joules and calories is their conversion factor. One calorie (the small calorie) is equivalent to approximately 4.184 joules.

In nutritional contexts, where the calorie is actually a kilocalorie, one food calorie is equivalent to approximately 4184 joules.

In most situations and conversions, the so-called "Thermochemical calorie" is used, which is equal to exactly 4.184 joules.