How to convert energy in joules (J) to calories (cal).
Small & large calories
Small calorie (cal) is the energy needed to increase 1 gram of water by 1°C at a pressure of 1 atmosphere.
Large calorie (Cal) is the energy needed to increase 1 kg of water by 1°C at a pressure of 1 atmosphere.
Large calorie is also called food calorie and is used as a unit of food energy.
How to convert from joules to calories
Joules to thermochemical calories
1 calth = 4.184 J
The energy in thermochemical calories E(calth) is equal to the energy in joules E(J) divided by 4.184:
E(cal) = E(J) / 4.184
Example
Convert 600 joules to thermochemical calories.
E(cal) = 600J / 4.184 = 143.4 calth
Joules to 15°C calories
1 cal15 = 4.1855 J
The energy in 15°C calories E(cal15) is equal to the energy in joules E(J) divided by 4.1855:
E(cal15) = E(J) / 4.1855
Example
Convert 600 joules to 15°C calories.
E(cal15) = 600J / 4.1855 = 143.352 cal15
Joules to large/food calories
1 Cal = 4.184 kJ = 4184 J
The energy in large/food calories E(Cal) is equal to the energy in joules E(J) divided by 4184:
E(Cal) = E(J) / 4184
Example
Convert 600 joules to food calories.
E(Cal) = 600J / 4184 = 0.1434 Cal