How to convert energy in calories (cal) to joules (J).
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 calories to joules
Thermochemical calories to joules
1 calth = 4.184 J
The energy in joules E(J) is equal to 4.184 times the energy in thermochemical calories E(calth):
E(J) = 4.184 × E(calth)
Example
Convert 300 calth to joules.
E(J) = 4.184 × 300calth = 1255.2 J
15°C calories to joules
1 cal15 = 4.1855 J
The energy in joules E(J) is equal to 4.1855 times the energy in 15°C calories E(cal15):
E(J) = 4.1855 × E(cal15)
Example
Convert 300 cal15 to joules.
E(J) = 4.1855 × 300cal15 = 1255.65 J
Large/food calories to joules
1 Cal = 4.184 kJ = 4184 J
The energy in joules E(J) is equal to 4184 times the energy in large/food calories E(Cal):
E(J) = 4184 × E(Cal)
Example
Convert 0.3 Cal to joules.
E(J) = 4184 × 0.3 Cal = 1255.2 J