Calculator: kJ to kcal converter How to convert kJ and kcal

Calculator: kJ to kcal converter How to convert kJ and kcal

What are kilocalories (kcal) and kilojoules (kJ)? Are you getting lost in the numbers? Our converter will help you.
Kilocalories and kilojoules conversion
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Calculator: converting kJ to kcal

When we perceive the energy we supply to the body, we can orient ourselves on the basis of two units. These are calories and joules. Kilocalories and kilojoules to be precise.

We have already come across both units. 

We see these values on food packaging every day. They are provided for the needs of consumers and to inform them about the nutritional data (protein, fat, sugars, etc.) and energy values.

The energy value must be given in both kJ (kilojoules) and kcal (kilocalories).

The naming of these units is mandatory.

They are KILO-calories - although in everyday life we refer to them as calories.

But what relevance do these values have for us, i.e. for the average consumer?

The human body has a need for nutrients and energy from birth, and indeed from conception and the embryonic and fetal periods. Of course, after all, they are necessary for the running of everything in the organism.

Even when a person is doing nothing, just lying around, sleeping, not thinking about anything ("difficult to perform inactivity") his body has a basic energy need. 

And it gets its energy from food in terms of ingested proteins, fats and sugars.

Naturally, in addition to these essential nutrients, we also need important vitamins and minerals. Water.

But back to energy.

Energy can be expressed in two values, namely:

  • Kilocalorie = kcal (1 kcal = 1000 cal)
  • Kilojoule = kJ (1 kJ = 1000 J)

When converting between units, we can use a simple formula where 1 kilocalorie equals 4.184 kilojoules. 

Conversion between kcal and kJoule:

  • 1 kcal = 4,184 kJ
  • 1 kJ = 0,2388 kcal
  • Kilocalorie = 4184 J

For a rough calculation, it would be enough if we remember that 1 kcal has approximately 4.2 kJ.

To make it easier, you can calculate the conversion in our calculator/converter.

And what is that calorie and joule?

A calorie, as a unit of energy, defines the energy required to give one gram of water to raise its temperature by 1 °C from 14.5 °C to 15.5 °C.

Joule (read joule) is the designation of a unit of work and energy. 

One Joule is equal to the kinetic energy of a kilogram of mass moving at a speed of one metre per second, and one Joule is equal to the work, equal in magnitude to 1 newton, exerted on a body along a path of one metre.

Complicated. But for easy understanding... 

Basically, an adult male should take in approximately 9,200 to 10,050 kJ = 2,198 to 2,402 kcal of energy during the day during normal activities.

For women this value is slightly lower, approximately 7530-8370 kJ = 1799-2000 kcal.

The basal energy requirement is about 65% of the total energy expenditure. As we have already stated, although our body does not exert anything externally, it has an energy requirement to maintain basic life functions and in a resting state.

Of course, we are all different, unique, and this needs to be taken into account when it comes to energy. Therefore, height, weight, and age are taken into account in the calculations.

What about the remaining 35 percent of the energy, you ask?

It is reported that about 10% goes into food processing and about 25% into physical activity.

So, our body is energy dependent and needs to be supplied with a total amount of energy. 

And we all know it. 

If there is too much food, energy is stored, so we gain weight. 

On the contrary, if the diet is low, we lose weight.

The important/rational/reasonable thing is to be somewhere in the middle and have a balanced daily energy intake and expenditure.

Interesting information on the topic can also be found in the articles:

Important notice:

Please remember that the results of our health calculators and analyzers are for guidance purposes only. They are not a substitute for a professional examination or the advice of a doctor, pharmacist or other health care professional.

Each person is unique, and everyone's needs may vary. Calculators and analyzers have limitations and do not provide a comprehensive individual view of health.

Their use is at your own risk. Neither the site operator nor the author is responsible for misuse and misinterpretation of information obtained through their use. By using the calculators and analyzers, you agree to these terms and conditions and neither the operator nor the author shall be liable for any consequences.

You are advised to consult a professional for your medical condition. Remember that health is an important topic and any decisions should be made in consultation with a professional.

This calculator/analyzer is not a medical tool or medical aid. Consult your doctor about your health problem.

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