Calories to Kilojoules (kJ) conversion

Calories (cal) to kilojoules (kJ), energy conversion calculator and how to convert.

Calories to kilojoules conversion calculator

Select calorie unit type, enter the energy in calories and press the Convert button:

Select calorie unit type:	Small thermochemical calories Small 15°C calories Large/food calories
Enter energy in calories:
Energy result in kilojoules:		kJ

kJ to calories conversion ►

Calories to Kilojoules

One calorie is equal to the heat needed to raise the temperature of one gram of water from 14.5 to 15.5 degrees Celsius. When measuring the energy content in foods, the large calorie, or kilocalorie is used, but it's often still just called a "calorie." When both the calorie and large calorie are used in the same context it is common to refer to the calorie as a "small calorie."

Calories can be abbreviated as cal; for example, 1 calorie can be written as 1 cal.

One kilojoule is equal to 1,000 joules, which are the energy equal to the force on an object of one newton at a distance of one meter. The kilojoule is a multiple of the joule, which is the SI derived unit for energy. In the metric system, "kilo" is the prefix for 10³. Kilojoules can be abbreviated as kJ; for example, 1 kilojoule can be written as 1 kJ.

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 kilojoules

Thermochemical calories to kJ

1 cal_th = 0.004184 kJ

1 kJ = 239.005736 cal_th

The energy in kilojoules E_(kJ) is equal to the energy in thermochemical calories E_(calth) divided by 239.005736:

E_(kJ) = E_(calth) / 239.005736

Example

Convert 300 cal_th to kilojoules.

E_(kJ) = 300cal_th / 239.005736 = 1.2552 kJ

15°C calories to kJ

1 cal₁₅ = 0.0041855 kJ

1 kJ = 238.9201 cal₁₅

The energy in kilojoules E_(kJ) is equal to the energy in 15°C calories E_(cal15) divided by 238.9201:

E_(kJ) = E_(cal15) / 238.9201

Example

Convert 300 cal₁₅ to kilojoules.

E_(kJ) = 300cal₁₅ / 238.9201 = 1.25565 kJ

Large/food calories to kJ

1 Cal = 4.184 kJ

1 kJ = 0.239 Cal

The energy in kilojoules E_(kJ) is equal to 4184 times the energy in large/food calories E_(Cal):

E_(kJ) = 4.184 × E_(calth)

Example

Convert 0.3 Cal to kilojoules.

E_(kJ) = 4.184 × 0.3 Cal = 1.2552 kJ

kJ to calories conversion ►