This cable length calculator finds the length of a conductor from its measured resistance and cross-sectional area, using the metal’s resistivity. Enter the values above.
Formula
Length = R × A ÷ ρ (ρCu ≈ 1.68×10⁻⁸ Ω·m)
Example
R = 2 Ω, A = 2 mm² copper: L = 2 × 2×10⁻⁶ ÷ 1.68×10⁻⁸ = 238 m.
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Frequently Asked Questions
How do I calculate cable length from resistance?
Multiply the measured resistance by the cross-section area and divide by the metal’s resistivity: L = R A / rho.
Why estimate cable length this way?
It helps locate the distance to a fault or check a reel’s length without physically measuring it.
What resistivity should I use?
About 1.68e-8 ohm-meter for copper and 2.82e-8 for aluminum.