Topic summary
Units of mass
Extracted from the Wikipedia article Mass.
Units of mass
The International System of Units (SI) unit of mass is the kilogram (kg). It is defined in terms of three constants, Planck constant, the speed of light, and the definition of the second (itself defined by fixing the caesium hyperfine frequency). The specific values of these constants were selected to closely approximate the older definition of the kilogram, the platinum–iridium International Prototype of the Kilogram.