Calories (thermoc.)
A thermochemical calorie (cal_th) is defined as exactly 4.184 joules. It is roughly the energy needed to warm one gram of water by one degree Celsius.
Therms (UK)
The therm (UK) is a unit of heat energy primarily used in the United Kingdom to measure the energy content of natural gas. It is defined as 100,000 British thermal units (BTUs) which is approximately 105.5 megajoules (MJ).