An intrinsic property of a material equal to the resistance per metre of material with cross-sectional area of one square metre:

where R is the resistance, A the cross-sectional area, and L the length. Resistivity depends only on the nature of the material whereas resistance depends not only on the material but on its length and cross-sectional area.

Resistivity is the reciprocal of conductivity: the lower the resistivity of a material the better conductor it is. Materials can be classified as conductors, semiconductors, or insulators according to their resistivities (see table). In semiconductors, the higher the doping level the lower the resistivity. See also surface resistivity.