Science · 47 calculators
Resistivity Calculator
Resistance describes a particular object; resistivity describes the material it is made of. Turning one into the other is a matter of geometry.
Resistivity
17
- Conductivity
- 58.8235
- Resistance per metre
- 0.034
- Resistance per kilometre
- 34
- Compared with copper
- 1.0119
Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.
The formula this calculator uses
rho = R x A / L
- rho
- Resistivity, the material property independent of the object's shape
- R
- The measured resistance of the sample
- A
- The cross sectional area of the sample
- L
- The length over which the resistance was measured
How to check the result by hand
- 1
Measure the resistance across a known length
The resistance must be measured over exactly the length you put in the formula. Here 3.4 ohms over 100 metres.
- 2
Convert the cross section to square metres
If the area is in square millimetres, divide by a million. Half a square millimetre is 0.0000005 square metres. This is the step that most often goes wrong.
- 3
Multiply resistance by area and divide by length
3.4 times 0.0000005 is 0.0000017, and dividing by 100 gives 0.000000017 ohm metres.
- 4
Rescale to nano ohm metres
Multiply by a billion to get 17. Working in nano ohm metres keeps the figures readable and comparable with published tables.
- 5
Compare against the standard for the material
Copper is about 16.8, so this sample reads 1.0119 times that. A much larger ratio points to an alloy, impurities or an overstated cross section.
For worked examples, common mistakes and the limits of this formula, read the full How To Calculate Resistivity page.