How Many Joules in a Calorie: Joules to Calories (J to cal) and Calories to Joules (cal to J) Conversion
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Conversion Formulas
Feel free to convert joules to calories (J to cal) and calories to joules (cal to J) using our conversion chart and conversion calculator, and learn the relationship between these two units.
Conversion of joules to calories (J to cal) and vice versa is an easy one since both units are units of energy. However, there is also a danger of confusion since the term "calorie" has two different definitions.
But, actual conversion is very easy since the calorie (after figuring out which calorie we are talking about) features a standardized value given in Joules (J).
The small calorie or gram calorie (often abbreviated as "cal") is defined as the amount of energy needed to increase the temperature of one gram of water by one degree Celsius (C) (or one Kelvin(K))  more accurate definition was to increase the temperature of one gram of water from 14.5°C to 15.5°C, but in modern times this is often omitted.
The large calorie, food calorie, or kilogram calorie (also often abbreviated as "cal") is defined as the amount of energy needed to increase the temperature of one kilogram of water by one degree Celsius (C) (or one Kelvin (K)).
Obviously, one large calorie equals 1000 small calories  and they are both often written as simply "cal" or "calorie".
In food science, nutrition, cooking, dieting, and similar, the term "calorie" and the symbol "cal" almost always refer to the large unit. In order to avoid confusion, many authors capitalize the letter "C" and write "Calorie" and "Cal", but this convention is not standardized.
In physics, chemistry, and other sciences, the term "calorie" or "cal" refers to a small calorie or simply  a calorie.
Note: in the rest of this article, we will write "Calorie" or "Cal" for large calories and "calorie" or "cal" for small calories.
Thus, the relation between Cal and cal is:
1 Cal = 1000 cal = 1 kcal
This is the reason why Cal or Calorie is often called kilocalorie.
The actual relation between calories, Calories, and Joules varied over time, but now this relation is defined as:
1 cal = 4.184 J
1 Cal = 1000 cal = 4184 J = 4.184 kJ
Joules to Calories (J to cal) and Calories to Joules (cal to J) Conversion Examples
Convert 100 cal to Joules:
In order to convert 100 cal to joules, we can write:
E = 100 cal = 0.1 kcal = 0.1 Cal = 100 * 4.184 J = 418.4 J
So, the energy (E) of 100 cal equals 418.4 J
Convert 160 Joules to calories:
In order to convert 160 Joules to calories, we can write:
E = 160 J = 160 / 4.184 cal = 38.24 cal = 0.03824 Cal
So, the energy (E) of 160 Joules equals 38.24 cal.
If we have a sandwich consisting of 50g of protein, 100g of carbs, and 20g of fats, how much energy is that?
This example shows the importance of distinguishing between Cal and cal  again, many people when talking about energy in food use cal while referring to kcal or Cal.
So, 1g of protein in the human body equals 4 kcal (Cal), 1g of carbs equals 4 kcal (Cal) and 1g of fat equals 9 kcal (Cal).
So, we can write:
E = 50g * 4 kcal/g + 100g * 4 kcal/g + 20g * 9 kcal/g = 200 kcal + 400 kcal + 180 kcal
E = 780 kcal = 780 Cal = 780.000 cal = 3263520 J = 3263.52 kJ = 3.26352 MJ
Note: most cooks and nutritionists would write the result as E = 780 cal (these are large calories) and not E = 780 kcal (small calories, which is a scientifically correct way of writing). This is plenty of energy and the worst thing is that is actually a small sandwich :)
Joules to Calories (J to cal) and Calories to Joules (cal to J) Conversion Calculator
In order to convert joules to calories (J to cal) and calories to joules (cal to J) feel free to use this conversion calculator  write the value that You have and click 'Calculate' to convert it:
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Joules to Calories (J to cal) and Calories to Joules (cal to J) Conversion Charts
Here are some joules to calories (J to cal) and calories to joules (cal to J) quick conversion charts to aid You with units' conversions:


For more values, please, use the conversion calculators.