Electrical Resistivity Converter
Electrical resistivity measures how strongly a material opposes current, with the SI unit of the ohm-meter (ohm.m). Engineers often use smaller units such as ohm-centimeter, microohm-centimeter, or the wire-table unit ohm-square-millimeter per meter. This converter reduces any of these to ohm-meters as a common base, then converts out, using exact length factors. For reference, annealed copper has a resistivity near 1.68e-8 ohm.m. Because values are tiny, results below 0.005 are shown in scientific notation.
Resistivity conversion
Base value (ohm.m) = input * factor(from unit)
Output = base value / factor(to unit)
1 ohm.cm = 0.01 ohm.m
1 uohm.cm = 1e-8 ohm.m
1 ohm.mm2/m = 1e-6 ohm.m
The unit ohm.mm2/m treats area in square millimeters (1e-6 m2) over a length in meters, giving 1e-6 ohm.m, identical to the microohm-meter.
Resistivity context
- The SI unit of resistivity is the ohm-meter (ohm.m).
- Annealed copper has a resistivity of about 1.68e-8 ohm.m at 20 degrees Celsius.
- Resistivity is the reciprocal of conductivity, measured in siemens per meter.
- The wire unit ohm.mm2/m equals the microohm-meter (1e-6 ohm.m).
- Resistivity rises with temperature for most metals.
Resistivity: frequently asked questions
What is the SI unit of electrical resistivity?
The ohm-meter (ohm.m). It is the resistance of a unit cube of material measured between opposite faces, and it equals resistance times area divided by length.
Why does ohm.mm2/m equal a microohm-meter?
Resistivity equals resistance times area over length. With area in square millimeters (1e-6 m2) and length in meters, 1 ohm.mm2/m is 1 ohm times 1e-6 m2 over 1 m, which is 1e-6 ohm.m, the microohm-meter.
How do I convert ohm.cm to ohm.m?
Multiply by 0.01, because one centimeter is 0.01 meter and resistivity scales linearly with the length unit. So 1 ohm.cm is 0.01 ohm.m.
What is copper's resistivity?
Annealed copper is about 1.68e-8 ohm.m at 20 degrees Celsius, or equivalently about 1.68 microohm-cm. The exact value depends on purity and temperature, so enter your own figure for precise work.
Is resistivity the same as resistance?
No. Resistance depends on the object's shape and size; resistivity is an intrinsic material property. Resistance equals resistivity times length divided by cross-sectional area.
Official sources
- NIST Special Publication 811: Guide for the Use of the International System of Units.
- NIST Office of Weights and Measures: SI Units.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.