Voltage Drop & Wire Sizing
Everyday & OtherCalculate electrical voltage drop, percentage loss, and end-of-circuit voltage for copper and aluminum conductors according to National Electrical Code (NEC) 3% standards.
Voltage at load: 115.24 V · Warning: Exceeds 3% branch circuit drop limit
About this calculator
As electric current flows through long wire conductors, internal electrical resistance causes voltage to drop along the length of the circuit. Excessive voltage drop causes lighting flicker, motor overheating, and electronics failure.
The National Electrical Code (NEC) recommends keeping total voltage drop under 3% for branch circuits. This calculator computes voltage drop for AC single-phase, AC 3-phase, and DC circuits across standard AWG wire gauges (14 AWG through 4/0).
How It Works & Formula
Single-Phase / DC Voltage Drop = (2 × K × I × L) / CM, where K is conductor resistivity (12.9 Ω·cmil/ft for copper, 21.2 for aluminum), I is current in Amperes, L is one-way distance in feet, and CM is wire circular mil area.
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