A calorimeter constant (denoted C) is a constant that quantifies the heat capacity of a calorimeter.  It may be calculated by applying a known amount of heat to the calorimeter and measuring the calorimeters corresponding change in temperature.  In SI units, the calorimeter constant is then calculated by dividing the change in enthalpy (ΔH) in joules by the change in temperature (ΔT') in kelvins or degrees Celsius:
The calorimeter constant is usually presented in units of joules per degree Celsius (J/°C) or joules per kelvin (J/K).  Every calorimeter has a unique calorimeter constant.