The resistivity of a material is usually denoted by the lower-case Greek letter rho (ρ) and is given by RS/l, where R is the resistance of a uniform specimen of the material, having a length l and a cross-section area S. The units of ρ are ohm meters. Its reciprocal quantity is electrical conductivity.
Also the resistivity is the magnitude of the electric field divided by the magnitude of the current density.
In general, electrical resistivity of metals increases with temperature, while the resistivity of semiconductors decreases with temperature.
Some materials lose all electrical resistivity under certain conditions; this effect is known as superconductivity.
The table of resistivity for various materials (at 20 degree):
| Material | Resistivity (Ohm-meters) |
| Silver | 1.59 x 10-8 |
| Copper | 1.7 x 10-8 |
| Gold | 2.44 x 10-8 |
| Aluminum | 2.82 x 10-8 |
| Tungsten | 5.6 x 10-8 |
| Iron | 10 x 10-8 |
| Platinum | 11 x 10-8 |
| Lead | 22 x 10-8 |
| Nichrome (A nickel-chromium alloy commonly used in heating elements) | 1.50 x 10-6 |
| Carbon | 3.5 x 10-5 |
| Germanium | 0.46 |
| Silicon | 640 |
| Glass | 1010 to 1014 |
| Hard rubber | approximately 1013 |
| Sulfur | 1015 |
| Quartz (fused) | 75 x 16 |