In chemistry we measure heat using two different units: calories and
joules. A calorie is defined as the amount of energy needed to raise
the temperature of one gram of water one degree Celsius. The “calorie” you are most familiar
with is used to measure the energy content of food. This “calorie” is actually
a kilocalorie (1000 calories) and is written with a capital C to distinguish
it from the calorie used in chemistry.
The Calories listed
for this candy bar
The other unit used to measure heat is the joule. The joule is the
SI (System International) unit. In this juice label from Amsterdam you can see that energy (“energie”) is given in kilojoules and kilocalories.
To convert between calories and joules:
1 Calorie (kcal) = 1000 calories (cal) = 4184 joules (J) = 4.184 kilojoules
or use this chart: