Calculate voltage drop in electrical wiring. Enter voltage, current, wire gauge, and run length to find voltage drop and NEC compliance.
Excessive (>5%)
| Voltage Drop | 7.90 V |
| Drop Percentage | 6.58% |
| Voltage at Load | 112.10 V |
| NEC Status | Excessive (>5%) |
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VD = (2 × K × I × L) / CM (single-phase)
K = 12.9 (copper), 21.2 (aluminum)
L = one-way length (ft), CM = circular mils
Voltage drop is the reduction in voltage in an electrical circuit between the source and load, caused by resistance in the wire. NEC recommends max 3% for branch circuits, 5% total.
VD = (2 × K × I × L) / CM, where K = resistivity constant, I = current (amps), L = one-way length (feet), CM = wire cross-section (circular mils).
NEC recommends no more than 3% voltage drop on branch circuits and 5% total (feeder + branch combined).
Yes. Copper has lower resistivity (K=12.9) than aluminum (K=21.2), resulting in less voltage drop for the same wire size.
Calculations are for educational purposes only. Consult a qualified financial advisor for personalized advice.