In science, the erg is an obsolete unit of energy. It is part of the centimeter-gram-second system of units (cgs system) and defined as the work necessary to move a mass over 1 cm against a force of 1 dyne. The SI unit of energy is the joule (J).
- 1 erg = 1 dyne cm = 1 g (cm/s)2 = 10−7 kg (m/s)2 = 10−7 J
An erg is an extremely small amount of energy. One erg would heat a 10-ounce (300 g) glass of water by only 0.1 billionths of a degree celsius.