The standard unit of mass in the metric system is the kilogram (kg). It serves as the base unit for measuring mass and is widely used in scientific, industrial, and everyday contexts. One kilogram is defined as being equal to the mass of the International Prototype of the Kilogram, which was a physical object made of platinum and iridium, until the definition was recently redefined based on fundamental constants. The metric system, which uses the kilogram, is based on decimal multiples, making it easier to convert between units, such as grams (g) and metric tons, ensuring precision in measurements across various fields.