The international unit of energy is the joule. Its derivatives - kilojoule and megajoule - are obtained by increasing the joule by 1,000 and 1,000,000 times, respectively. Since energy can be found in different branches of physics in different ways, depending on its purpose, the Joule can be expressed in many other units. So, for example, in thermodynamics, work, heat and energy are one and the same quantity, which makes it possible to translate Joules into calories and kilocalories. In electricity, energy is the work of amperage, which is equal to power per unit time. Therefore, the ratio of power units to time units, for example, Watt / hour, is also proportional to Joules. In atomic and nuclear physics, Joules are not relevant, since they are too large for accurate measurements, therefore, electron volts are used. Along with them, there is a unit of energy - erg, which determines the work of a force by moving the point of its application. How to use the energy converter: Suppose you set out to calculate how much energy in joules contains 400 kilocalories. To do this, enter the number 400 in the string "kcal" and press Enter. It will be converted to all available units, and the line "J" will show the desired number.