Physics

Wire Resistance Calculator

Find a wire's resistance from material, length and cross-section.

Resistivity (Ω·m)

Length

Cross-section area (mm²)

Calculated Output

Resistance (Ω) 0.336

Formula: R = ρ·L ÷ A

Step-by-Step Breakdown

1. Values used:

2. Resistivity = 0 Ω·m

3. Length = 50

4. Cross-section area = 2.5 mm²

6. Resistance = 0.336Ω

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The math behind it

R = ρ·L ÷ A. Copper's resistivity is about 1.68 × 10⁻⁸ Ω·m.

50 m of 2.5 mm² copper → about 0.34 Ω.

Why does long thin wire heat up?

Higher resistance dissipates more power (P = I²R) for the same current.