What is 1 joule equal to in calories?

What is 1 joule equal to in calories? The short answer is that 1 joule is equal to 0.239005736 calories. A joule is a unit of energy in the International System of Units (SI), while a calorie is a pre-SI metric unit of energy. Specifically, 1 joule is defined as the work done by a force of 1 newton moving an object 1 meter. 1 calorie is defined as the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius. Through precise scientific measurements and calculations, the conversion factor between joules and calories has been determined to be 1 joule = 0.239005736 calories.

Defining the Joule

The joule is the standard unit of energy in the International System of Units (SI). It is defined as the work done by a force of 1 newton exerted over a distance of 1 meter. A newton is the SI unit of force, defined as the amount needed to accelerate 1 kilogram of mass by 1 meter per second squared. So 1 joule is the amount of energy transferred when a 1 newton force moves an object 1 meter.

The joule was named after the English physicist James Prescott Joule. Joule conducted experiments in the 1840s demonstrating that mechanical energy could be converted to heat. His famous experiment involved stirring water with paddles powered by falling weights. Joule measured the temperature increase of the water resulting from the mechanical stirring. Through careful experimentation, he was able to quantify the relationship between mechanical work and heat.

Joule’s experiments helped establish the law of conservation of energy – the principle that energy can be converted between forms but is never lost. They also demonstrated the equivalence between various forms of energy. Joule’s quantitative measurements of mechanical equivalent of heat helped define the joule as a unit of energy.

The joule became an official SI unit in 1971. It is defined based on standards of the meter (distance) and the kilogram (mass). Precisely defined standards for mass, distance, and time enable an exact definition of force and energy in SI units.

Joule Definition Summary

– The joule (J) is the SI unit of energy
– 1 joule is the energy transferred when a force of 1 newton moves an object 1 meter
– Defined in terms of standards for meter and kilogram
– Named after James Prescott Joule, pioneer of energy experiments

Defining the Calorie

The calorie is a pre-SI metric unit of energy that is based on the amount of heat. The word “calorie” comes from the Latin word “calor”, meaning heat. A calorie is defined as the amount of energy required to raise the temperature of 1 gram of water by 1 degree Celsius. This is measured at standard atmospheric pressure.

Originally, the calorie was defined in relation to the heating of water. In the late 19th century, measurements determined that raising 1 gram of water 1°C required 4.1868 joules of energy. Based on this conversion factor, the calorie was redefined more precisely as 4.1868 joules.

There are two other common definitions related to the calorie:

– 15 degree calorie (cal15): The amount of energy to raise 1 g of water from 14.5°C to 15.5°C at standard atmospheric pressure. Equal to 4.1855 joules.

– Thermochemical calorie (calth): The amount of energy to raise 1 g of water from 15.5°C to 16.5°C at standard atmospheric pressure. Equal to 4.184 joules.

This variation in calorie definitions can cause confusion and inaccurate conversions. Today the 4.1868 joule calorie is the standard definition used for nutrition information. Food energy is often given in large Calories (kilocalories) rather than smaller calories.

Calorie Definition Summary

– The calorie (cal) is a metric unit of energy originally based on heating water
– 1 calorie is the energy needed to raise 1 gram of water by 1°C
– Defined as 4.1868 joules by precise measurements
– Other definitions exist based on raising 1 g water across different temperature increments
– The 4.1868 joule definition is standard for nutrition information

Converting Between Joules and Calories

Now that we have clearly defined the joule and calorie units, we can precisely convert between them. As mentioned above, the standard calorie is defined in terms of the joule.


1 calorie = 4.1868 joules

This means:

1 joule = 0.239005736 calories

This conversion factor allows us to convert energy amounts between joules and calories. For example:

100 joules x (1 calorie/4.1868 joules) = 23.90057360 calories

250 calories x (4.1868 joules/1 calorie) = 1046.7 joules

To convert joules to calories, multiply joules by 0.239005736
To convert calories to joules, multiply calories by 4.1868

This precise conversion factor between the units comes from advanced scientific measurements relating amount of heat to mechanical energy. We can confidently use the conversion in calculations and unit conversions involving energy.

Joules to Calories Conversion Summary

– 1 joule = 0.239005736 calories
– To convert joules to calories: multiply joules by 0.239005736
– To convert calories to joules: multiply calories by 4.1868
– The conversion factor is based on precise measurements relating heat and mechanical energy

Comparing Applications of the Joule and Calorie

The joule and calorie are both important energy units that are used in different applications. Some key differences in practical usage:

Joules are used to measure energy in scientific contexts and in SI units. Things like kinetic energy, potential energy, and thermodynamic energy are often measured in joules. For example, a 150 J energy pulse from a laser. Or a 75 J kinetic energy of a tennis ball in motion.

Calories are more commonly used in nutrition facts listings and food energy measurements. Nutritional energy from fat, carbohydrates, protein, and alcohol is given in food Calorie amounts. For example, a 340 Calorie serving of bread. Or a 200 Calorie slice of cake.

Joules are standard units across all sciences. Calories relate specifically to nutritional biochemistry and human metabolism. While joules can measure all energy transfers, calories specifically apply to energy available for organisms.

Additionally, joules represent smaller amounts than Calories. Nutrition labels use Calories, where 1 Calorie = 1000 calories = 4184 joules. So a 340 Calorie serving of bread contains 1,423,760 joules.

In physics, joules are used in the most fundamental definitions, like work, power, and thermodynamic values. Calories are practical for tangible applications like diet, weight loss, and metabolic activity.

Comparison Summary

– Joules are used for energy amounts in physics and other sciences
– Calories are used for nutritional energy values of foods
– Joules apply broadly to all energy transfers
– Calories relate specifically to human metabolism
– Nutrition Calories are 1000 small calories, or ~4184 joules

Example Conversions Between Joules and Calories

Here are some examples converting energy amounts between joules and calories using the conversion factor:

1) A 75 kilojoule serving of almonds:

75,000 joules x (1 calorie/4.1868 joules) = 17,905 calories

So 75 kilojoules of almonds contains 17,905 calories

2) A 340 Calorie bowl of oatmeal:

340 Calories x (4.1868 joules/1 calorie) x (1000 cal/1 Cal) = 1,423,312 joules

So 340 Calories is 1,423,312 joules.

3) The kinetic energy of a tennis ball is 150 joules. In calories, that is:

150 joules x (1 cal/4.1868 joules) = 35.8 calories

So a tennis ball with 150 J of kinetic energy has 35.8 calories of energy.

4) A 185 pound person climbing 10 flights of stairs burns 200 Calories:

200 Calories x (4.1868 joules/1 calorie) x (1000 cal/1 Cal) = 837,360 joules

So 200 Calories expended is 837,360 joules of energy.

Being able to convert between joules and calories allows calculation of both scientific and nutritional energy values. The precise conversion factor helps relate the fundamental physics of energy to real world applications.

Comparing Nutritional Content in Joules and Calories

Nutrition labels on foods show the calorie content, which allows people to track their nutritional intake. However, the same nutrition information can be displayed in joules using the unit conversion.

Here is an example nutritional label with both Calories and joules:

Nutrient Amount Calories Joules
Total Fat 10 g 90 Cal 377,820 J
Saturated Fat 3 g 27 Cal 113,346 J
Trans Fat 1 g 9 Cal 37,781 J
Cholesterol 15 mg 0 Cal 0 J
Sodium 350 mg 0 Cal 0 J
Total Carbohydrates 45 g 180 Cal 754,360 J
Dietary Fiber 4 g 0 Cal 0 J
Sugars 12 g 48 Cal 201,424 J
Added Sugars 4 g 16 Cal 67,141 J
Protein 5 g 20 Cal 83,736 J

This allows people to understand the joule values for nutritional intake alongside the traditional calorie amounts. The conversions put the Calorie energy units into their equivalent SI joule units. While calories will likely remain the most popular unit for nutrition, displaying joules provides scientific context for food energy.

Converting Exercise and Weight Loss

Calories are also very useful for quantifying exercise activities and weight loss goals. The calorie burn of various workouts helps people calculate their energy expenditure. And targeting a daily calorie deficit facilitates weight loss plans.

Again, we can convert Calories into joules to represent the same values according to international standard units.

Here are some examples:

– A 185 pound person doing 30 minutes on an elliptical machine burns 300 Calories. In joules, that is 300 Cal x 4184 J/Cal = 1,255,200 joules.

– A 140 pound person doing 45 minutes of vigorous swimming burns 500 Calories. In joules, that is 500 Cal x 4184 J/Cal = 2,092,000 joules.

– A weight loss goal to cut 500 Calories per day from diet is 2,092,000 joules per day of energy deficit.

– Losing 1 pound requires a 3500 Calorie deficit. In joules, that is 3500 Cal x 4184 J/Cal = 14,644,000 joules total deficit.

So a daily 500 Calorie deficit would lead to losing 1 pound in 7 days. Or in joule terms, a daily 2,092,000 joule deficit leads to a 14,644,000 joule total deficit to lose 1 lb.

Looking at Calories and their joule equivalents provides helpful insight into weight management and nutrition goals. The ability to convert between the units aids with calculating exercise energy expenditures and weight loss strategies.


In summary, 1 joule is equivalent to 0.239005736 calories. The joule is the SI unit of energy defined based on force and distance. The calorie originally related to heating water and is now defined in terms of joules.

The precise conversion factor enables translating between joules and calories for any energy application. Joules are used universally in sciences while calories are practical for nutrition and weight management. Knowing the relationship between units allows you to evaluate and convert energy amounts across disciplines.

Quick conversions:

– 1 joule = 0.239005736 calories
– 1 calorie = 4.1868 joules
– 1 food Calorie = 4184 joules

So if you know joules or calories of energy, you can easily convert between these units using the provided factors. Understanding both systems provides insight into the science of energy as well as practical applications for health, diet, and exercise.

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