Quick answer: voltage drop = circuit current × conductor resistance. Enter the one-way length, conductor, system type, and current, then check both volts lost and percentage at the load. Confirm the final design against the governing code and equipment limits.
Input Parameters
About This Calculator
- R = ρ × L / A
- 1φ: ΔV = 2 × I × R | 3φ: ΔV = √3 × I × R
- NEC recommends ≤3% branch, ≤5% total
How this voltage drop calculator works
Wire resistance: R = ρ × L / A where ρ(Cu)=0.0172, ρ(Al)=0.0282 Ω·mm²/m.
Voltage drop: ΔV = 2×I×R (single-phase) or ΔV = √3×I×R (three-phase). NEC recommends max 3% for branch circuits.
FAQ
Acceptable voltage drop?
≤3% branch, ≤5% total per NEC.
How to calculate?
ΔV = 2×I×R or √3×I×R for 3-phase.
How to reduce drop?
Larger wire, shorter run, or higher voltage.