Calories (thermoc.)
A thermochemical calorie, often abbreviated as cal_th, is a unit of energy that is primarily used in the field of chemistry. It is defined as the amount of energy required to raise the temperature of one gram of water by one degree Celsius at a pressure of one atmosphere, precisely defined as 4.184 joules.
Calories (Kilogram,I.T.)
The kilogram calorie is often referred to as the kilocalorie or Calorie with an uppercase 'C'). It is defined as the amount of energy required to raise the temperature of one kilogram of water by one degree Celsius at one atmosphere of pressure.