Voltage Drop Calculator

Voltage drop, drop %, and voltage at load end — single and 3-phase

Circuit Parameters

Phase

Wire Gauge

System Voltage

Load Current (A)

One-Way Length (ft)

Wire Material

Voltage Drop

6.58%

Voltage Drop

7.902 V

Voltage at Load

112.10 V

✗ Fail — Exceeds 5% — upsize wire or shorten run

Single-phase: VD = (2 × K × I × L) / CM

Three-phase: VD = (√3 × K × I × L) / CM

K = 12.9 (copper, 75°C)

K = 21.2 (aluminum, 75°C)

I = load current (amps)

L = one-way length (ft)

CM = circular mils

VD% = (VD ÷ V) × 100

NEC recommends <3% for branch circuits, <5% combined feeder + branch.