How is a calorie and thermal energy related?

Answer 1

One calorie is the thermal energy required to raise one gram of water by one deg C. (Note that in food, the calorie used is actually the kilocalorie. Also that one calorie = 4.2 Joules.)

Another Answer

The calorie is an older unit of measurement for energy and work. It was part of the centimetre-gram-second-ampere (cgsA) system, which has long been replaced by the SI system. The modern, SI, unit of measurement for energy and work is the joule.

Answer 2

Calories are a measure of energy gained from food while thermal energy is the energy produced by the movement of atoms and molecules within a substance. When food is metabolized, it releases thermal energy in the form of heat, which is why the calorie content of food is often associated with the energy it provides to the body.