Kilogram

The kilogram or kilogramme (symbol: kg) is the SI base unit of mass. It is defined as being equal to the mass of the international prototype of the kilogram. It is the only SI base unit that employs a prefix, and the only SI unit that is still defined in relation to an artifact rather than to a fundamental physical property. A kilogram’s weight is close to that of a one-liter plastic water or milk bottle when full.

The pound, being defined as exactly 453.59237 grams, results in the kilogram being approximately equivalent to 2.205 avoirdupois pounds in the Imperial system and the customary system of weights and measures used in the United States.