Wire Resistance Calculator
Find a wire's resistance from material, length and cross-section.
A wire's resistance grows with length and shrinks with thickness.
The math behind it
R = ρ·L ÷ A. Copper's resistivity is about 1.68 × 10⁻⁸ Ω·m.
Worked example
50 m of 2.5 mm² copper → about 0.34 Ω.
FAQ
Why does long thin wire heat up?
Higher resistance dissipates more power (P = I²R) for the same current.