The International (SI) System of Units published in 1960 used the kilogramme as the base unit of mass, and has been adopted by almost every country on earth (with a few notable the exceptions such as the United States). The kilogramme (derived from the Greek chilioi and gramma was named as a more practical measure of mass for larger quantities in trade, and came to be used as the base unit of mass in all metric measurement systems. In 1795 metric measurement systems were introduced in France and the gram was defined as "the absolute weight of a volume of pure water equal to a cube of one hundredth of a metre, and at the temperature of the melting ice".
It is the only SI unit that is defined by a physical object rather than a fundamental physical property that can be reproduced in laboratories.įor a short period the grave (also a metallic reference standard) was used to define one thousand grams, until it was replaced by the kilogram in 1799. The kg is defined as being equal to the mass of the International Prototype of the Kilogram (IPK), a block of platinum-iridium alloy manufactured in 1889 and stored at the International Bureau of Weights and Measures in Sèvres, France. The kilogram is almost exactly equal to the mass of one litre of water.
The kilogram is the base unit of mass in the International (SI) System of Units, and is accepted on a day-to-day basis as a unit of weight (the gravitational force acting on any given object).
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