Electrical Resistivity Converter
Convert electrical resistivity between Ω·m, Ω·cm, μΩ·cm, Ω·mm²/m, and statΩ·cm. Enter a resistivity value, then select the units to convert from and to.
Convert Electrical Resistivity Between Units
Electrical Resistivity Conversion Formula
Where:
- \(\rho_{\mathrm{from}}\) — the entered resistivity in the selected From unit
- \(\rho_{\mathrm{to}}\) — the converted resistivity in the selected To unit
- \(f_{\mathrm{from}}\) and \(f_{\mathrm{to}}\) — the units’ conversion factors to Ω·m
The calculator first expresses the entered value in Ω·m, then divides by the conversion factor for the requested unit. Its statΩ·cm factor does not match the physical CGS-to-SI conversion; see the limitation below.
Electrical Resistivity Conversion – Calculation Example
Example: Convert the default resistivity value, \(1.68\times10^{-8}\) Ω·m, to μΩ·cm. One μΩ·cm equals \(10^{-8}\) Ω·m.
\[ \rho_{\mathrm{to}}=(1.68\times10^{-8})\frac{1}{10^{-8}}=1.68\ \mu\Omega\cdot\mathrm{cm} \]
Result: 1.68 μΩ·cm.
How to use the calculator
- Enter a nonnegative number in Resistivity value. You can use decimal or scientific notation for very small values.
- Choose the unit of that number under From unit.
- Choose the unit you need under To unit.
- Read Converted Resistivity. The result includes the selected destination unit.
The default settings convert \(1.68\times10^{-8}\) Ω·m to 1.68 μΩ·cm. Select the same unit in both menus to keep the numerical value unchanged, apart from any display rounding.
What electrical resistivity means
Electrical resistivity, represented by \(\rho\), describes how strongly a material opposes electric current. A lower resistivity generally means a material is a better electrical conductor. Resistivity is a material property, whereas the resistance of a particular piece also depends on its dimensions. For a uniform conductor, \(R=\rho L/A\), where \(R\) is resistance, \(L\) is length, and \(A\) is cross-sectional area.
The SI unit is the ohm meter (Ω·m). Smaller units are often more convenient when reporting metals: the default value, representative of copper near room temperature, is 1.68 μΩ·cm. Ω·cm is also used for materials with higher resistivity, while Ω·mm²/m is convenient in wire calculations because length may be measured in meters and cross-sectional area in square millimeters. Changing units changes only the number used to express a resistivity, not the underlying material property.
Resistivity should not be confused with conductivity, its reciprocal, or with conductance, the reciprocal of a component’s resistance. If you are comparing component measurements rather than material properties, the Conductance Units converter may be more appropriate. For measurements expressed as current, use the Electric Current converter.
Unit factors and practical limits
For the four SI-derived units, the converter uses these factors to express one unit in Ω·m:
| Unit | 1 unit equals |
|---|---|
| Ω·m | 1 Ω·m |
| Ω·cm | 0.01 Ω·m |
| μΩ·cm | \(10^{-8}\) Ω·m |
| Ω·mm²/m | \(10^{-6}\) Ω·m |
These factors provide quick checks: 1 Ω·m is 100 Ω·cm, \(10^8\) μΩ·cm, or \(10^6\) Ω·mm²/m. When comparing published values, check that they refer to the same temperature and material condition. Resistivity often changes with temperature, and this converter performs no temperature correction.
Important CGS limitation: The calculator uses \(1\ \mathrm{stat\Omega\cdot cm}=8.98755179\times10^{11}\ \Omega\cdot\mathrm{m}\). The physical conversion is approximately \(8.98755179\times10^9\ \Omega\cdot\mathrm{m}\). Consequently, conversions involving statΩ·cm differ from the physical conversion by a factor of 100. Avoid using its statΩ·cm results for scientific or engineering work unless that factor is corrected.
The displayed result is rounded to 12 decimal places. Extremely small nonzero results may therefore appear as zero; if that happens, convert through a smaller unit or calculate with the factors above.
Frequently Asked Questions
How do I convert between resistivity units by hand?
Convert through Ω·m, keeping track of each unit’s multiplier. For example, 1 Ω·mm²/m equals 0.000001 Ω·m, while 1 μΩ·cm equals 0.00000001 Ω·m. Dividing those values shows that 1 Ω·mm²/m equals 100 μΩ·cm. A common mistake is treating mm² as a length rather than an area.
What is a good electrical resistivity for a conductor?
A lower resistivity is generally better when you want a conductor to minimize electrical losses. Near room temperature, copper is about 1.68 μΩ·cm and aluminum is about 2.65 μΩ·cm. There is no universal “good” value: cost, weight, corrosion resistance, temperature, and the material’s intended use also matter.
Can I calculate a material’s resistivity from a resistance measurement?
Yes. For a uniform sample, multiply its measured resistance by its cross-sectional area, then divide by its length. Use meters for length and square meters for area to obtain Ω·m. Contact resistance, uneven dimensions, and heating during measurement can distort the result, especially for low-resistance samples.
How do I convert resistivity to electrical conductivity?
Take the reciprocal of resistivity expressed in Ω·m; the conductivity will be in siemens per meter (S/m). For example, a resistivity of 0.00000002 Ω·m corresponds to 50,000,000 S/m. Do not take the reciprocal of a value in μΩ·cm without first converting its units, or the numerical answer will be wrong.
How much does temperature change electrical resistivity?
For many metals, resistivity increases as temperature rises. Near room temperature, copper’s resistivity changes by roughly 0.39% per °C, though the rate depends on material and temperature range. For a rough adjustment, apply that percentage to the difference from the reference temperature; use measured data when accuracy matters.
Can I use the statΩ·cm result for a scientific calculation?
Not without correcting it. This calculator’s statΩ·cm factor is 100 times the physical CGS-to-SI factor. A result converted from statΩ·cm into an SI-derived unit is 100 times too large; a result converted to statΩ·cm is 100 times too small. Use a verified conversion factor for scientific or engineering work.
Why does a nonzero resistivity sometimes display as zero?
The displayed number is rounded to 12 decimal places, so a sufficiently small result can appear as zero even when its calculated value is nonzero. This is especially likely when converting a metal’s resistivity to a much larger unit. Try a smaller unit, such as μΩ·cm, or calculate the result in scientific notation.