A Joule (J) is an International Standard (SI) of Units of energy, work, force, quantity of heat. It is equal to the energy transferred (or work done) to an object when a force of one newton acts on that object in the direction of its motion through a distance of one metre (1 newton metre or N·m): m2·kg·s-2. 1 J is equal to 1×10^7 erg (exactly), 0.2390 cal (gram calories), 9.4782×10^-4 BTU, 2.7778×10^-7 kilowatt-hour. 

kJ (Kilojoule) equals to one thousand Joules (J); MJ (MegaJoule) equals to one million (10^6) Joules (J)

Related Definitions in the Project: The Property and Unit