Wire Resistance Calculator

What Is a Wire Resistance Calculator?

Every conductor resists the flow of current, and that resistance depends on the material, the length, and the cross-sectional area of the wire. Our Wire Resistance Calculator applies the standard resistivity formula for copper and aluminum, with an optional temperature correction.

How the Calculation Works

$$\rho(T) = \rho_{20}\left[1 + \alpha (T - 20)\right]$$

$$R = \frac{\rho(T) L}{A}$$

Where:

• ρ(T) is the resistivity at the operating temperature
• ρ₂₀ is the resistivity at 20°C (copper 1.68 × 10⁻⁸ Ω·m, aluminum 2.82 × 10⁻⁸ Ω·m)
• α is the temperature coefficient (copper 0.00393, aluminum 0.00403 per °C)
• T is the conductor temperature in °C
• L is the length in meters
• A is the cross-sectional area in square meters

Worked Example

A 100 m copper conductor with a 2.08 mm² cross-section at 20°C gives R = (1.68 × 10⁻⁸ × 100) / (2.08 × 10⁻⁶) = 0.808 Ω. If the conductor runs at 60°C, the resistivity rises to 1.944 × 10⁻⁸ Ω·m and the resistance becomes about 0.935 Ω.

Related tools include the Wire Gauge Calculator, the Wheatstone Bridge Calculator, and the Work and Power Calculator.