Wire Voltage Drop
Calculate voltage drop over a 2-wire conductor given current, length, cross-section, and conductor material. Resistivity is pulled from our materials database with source attribution.
Limitations: Assumes 20°C conductor temperature. Higher operating temperature increases resistivity. For 3-phase or single-wire-return circuits, divide by the appropriate factor (3-phase line-to-line: multiply by √3 instead of 2; single-wire ground-return: use 1).
What to do next: NEC recommends keeping voltage drop ≤ 3% on branch circuits and ≤ 5% total (branch + feeder) for normal service. If your drop exceeds that, increase the wire gauge.
Assumes standard 20°C conductor temperature. For NEC compliance, ampacity limits, and derating, consult a licensed electrician or the NEC tables directly.