How to use the wire resistance calculator
Compute resistance and voltage drop of a wire. Enter material, length, diameter, current in the fields above; the resistance, voltage drop, power lost are computed instantly and plotted on the chart so you can see how the answer changes.
Formula
Variables
- rho — Material (Ω·m)
- L — Length (m)
- d — Diameter (mm)
- I — Current (A)
Worked example
With material = Copper, length = 50 m, diameter = 1.6 mm, current = 5 A, the calculator gives resistance ≈ 0.4177817 Ω; voltage drop ≈ 2.088909 V; power lost ≈ 10.44454 W.
Frequently asked questions
What is the formula for the wire resistance calculation?
Resistance (Ω) = rho × L / (π × (d / 2000)^2). Voltage drop (V) = [Resistance] × I. Power lost (W) = [Resistance] × I × I. Here rho is material (Ω·m), L is length (m), d is diameter (mm), I is current (A).
What inputs do I need for the wire resistance calculator?
You need material in Ω·m, length in m, diameter in mm, current in A. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use this calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.