Wire Resistance Calculator

About this calculator

This calculator finds a wire's electrical resistance using R = ρL/A — the material's resistivity (ρ) times length (L), divided by cross-sectional area (A) — accounting for the fact that longer, thinner wires resist current more than shorter, thicker ones, and that copper and aluminum have very different resistivity values.

Electricians and DIY builders use it to check whether a wire gauge is appropriate for a run length before voltage drop becomes a problem, and electronics hobbyists use it to predict resistance in custom wiring or heating-element designs where the wire itself is part of the circuit's behavior, not just a connector.