Voltage Drop Calculator (Residential)

Calculate voltage drop for residential wiring and check compliance with the NEC 3% recommendation.

Inputs

Wire Gauge (AWG)

One-Way Distance

Current

System Voltage

Tab to move between fields

Results

Voltage Drop

3.57 V

Drop Percentage2.98%

Voltage at Load116.43 V

NEC 3% Compliant1

Power Loss53.6 W

How to Use This Calculator

Select Wire Gauge (AWG) from the dropdown — lower AWG = thicker wire.
Enter One-Way Distance (ft) from panel to load.
Input Current (amps) drawn by the load.
Review Actual Voltage Drop (%) — NEC recommends keeping this below 3% for branch circuits.
If voltage drop exceeds 3%, select the next heavier AWG and recalculate.

How the result changes with One-Way Distance

One-Way Distance	Voltage Drop
101	4.81 V
351	16.72 V
650	30.97 V
900	42.88 V

What each input means

Wire Gauge (AWG): AWG wire gauge of the installed or planned conductor.
One-Way Distance: One-way distance from panel to the load in feet.
Current: Current draw of the circuit load in amps.
System Voltage: Nominal system voltage of the circuit.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Wire Gauge (AWG) = 12, One-Way Distance = 75, Current = 15, System Voltage = 120 = 4 input(s) provided
Calculate Voltage Drop
Voltage Drop
3.57 = 3.57
Calculate Drop Percentage
Drop Percentage
2.98 = 2.98
Calculate Voltage at Load
Voltage at Load
116.43 = 116.43

Engine last updated July 11, 2026.

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