About the Wire Resistance Calculator
Resistance of a length of wire from its material, cross-section and temperature.
Also known as: cable resistance, conductor resistance, resistivity calculator, ohms per metre.
How to use this calculator
- Enter material, cross-section, length, temperature.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
R = ρL / A · R_T = R₂₀(1 + α(T − 20))
Worked example
Using the values pre-filled in the calculator above:
- Material: Copper
- Cross-section = 2.5 mm²
- Length = 50 m
- Temperature = 20 °C
the calculator returns:
- Resistance: 0.336 Ω
- At 20 °C: 0.336 Ω
- Per metre: 0.00672 Ω/m
- Wire diameter: 1.784 mm