Voltage drop calculator
Estimate resistive voltage drop along outgoing and return conductors using entered resistivity.
Formula
R = 2Lρ/A; ΔV = IR; drop % = 100ΔV/V
One-way length: 100 ft · Cross-section: 2.5 mm² · Loop resistance (Ω) ≈ 2×(100 ft × 0.3048 m/ft)×(0.01724)÷((2.5 mm² × 0.000001 m²/mm²)×1000000) · Voltage drop (V) ≈ (10)×(0.42038016) · Voltage drop (%) ≈ (4.2038016)÷(120)×100
How to use
- Enter one-way length and wire cross-section.
- Set current, supply voltage and resistivity.
- Read the drop and loop resistance.
Examples
- 10 A through a 0.2 Ω loop drops 2 V.
Frequently asked questions
Why is length doubled?
The current travels through outgoing and return wires.
What does the default resistivity mean?
0.01724 Ω·mm²/m approximates annealed copper at 20 °C.
Does it check wiring compliance?
No. Temperature, connectors, AC reactance and ampacity require separate checks.
Sources
Updated: