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Wire Resistance Calculator

Calculate a wire's electrical resistance from its material, length, and cross-sectional area, in metric (m/mm²) or imperial (ft/in²) units.

Resistance
0.112 Ω
Resistivity used (Ω·mm²/m at 20°C)
0.0168

How it works

A wire's resistance follows R = ρ × L ÷ A, where ρ (rho) is the material's resistivity, L is the wire's length, and A is its cross-sectional area — a longer or thinner wire resists current more. Resistivity values used here are standard published figures at 20°C, in ohm·mm²/m: silver 0.0159, copper 0.0168, gold 0.0244, aluminum 0.0265, tungsten 0.0565, iron 0.0971, nichrome 1.1. These are fixed physical properties of each material, not facts that change over time.

Length and area are converted to meters and mm² (the units resistivity is published in above) before the formula runs, so switching the Metric/Imperial toggle rescales the displayed fields but gives the identical resistance either way.

Real wire (and especially alloys like nichrome, used in heating elements) can vary somewhat by purity, temperature, and manufacturing — treat this as a close estimate from textbook resistivity figures, not a spec-sheet-exact value for a specific product.

FAQ

Why does nichrome have so much more resistance than copper?

Nichrome (a nickel-chromium alloy) is deliberately chosen for heating elements and resistors precisely because its resistivity is roughly 65 times copper's — a short length gets hot from resistive heating at ordinary currents. Copper's very low resistivity is why it's used for wiring, where the goal is to move current with minimal loss instead.

Does temperature affect a wire's resistance?

Yes — nearly all metals become more resistive as they heat up. This calculator uses resistivity values at a fixed 20°C reference temperature, the standard convention for published tables, and doesn't model how resistance shifts if the wire runs hot in use.

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