A measure of the quantity of matter is called mass. The International System (SI), commonly known as the metric system, uses the kilogram as the base unit of mass, while the British imperial unit for the mass is the pound. In the United States, the pound is also used as the customary unit of mass.
In chemistry, matter is defined as anything that has mass and occupies space. Mass, which is one of the basic properties of matter, measures the amount of inertia an object contains. It is typically represented as the letter "m" in mathematical formulas. A derived unit for the mass is the gram. One kilogram is equivalent to 1000 grams.