6.02214179(30)×10^23

In chemistry and physics, the Avogadro constant (symbols: L, NA) is defined as the ratio of the number of entities (usually atoms or molecules) N in a sample to the amount of substance n (unit mole) through the relationship NA = N/n. Thus it is the proportionality factor that relates the molar mass of an entity, i.e. the mass per amount of substance, to the mass of said entity. The Avogadro constant expresses the number of elementary entities per mole of substance and it has the value 6.02214179(30)×10^23