Calories (20°C)
A Calorie (20°C) is sometimes referred to as a small calorie or gram calorie. It is a unit of energy defined as the amount of heat required to raise the temperature of one gram of water by one degree Celsius from 19.5°C to 20.5°C.
Calories (mean)
A mean calorie is a unit of energy that was historically used to quantify the amount of energy required to raise the temperature of one gram of water by one degree Celsius, approximately equal to 4.184 joules.