one commercial grade called Invar 36 it consists of approximately 36% nickel and 64% iron, has a melting point of 1427 C, a density of and a resistivity of . The invar range was described by Westinghouse scientists in 1961 as "30-45 atom per cent nickel".

Common grades of Invar have a coefficient of thermal expansion (denoted ?, and measured between 20 °C and 100 °C)