Calculate voltage drop in electrical circuits to ensure proper wire sizing and electrical safety

System Type:

Conductor Material:

Supply Voltage (V):

Typically 120V or 240V for residential

Current Load (A):

Circuit's maximum expected current

One-Way Length (ft):

Distance from source to load

Wire Size:

Maximum Permissible Voltage Drop (%):

NEC recommends max 3% for branch circuits

Enter parameters and click "Calculate" above

Note: This calculator follows basic Ohm's Law calculations. For critical applications, consult electrical codes and professionals.

Voltage Drop	-
Percentage Drop	-
Voltage at Load	-
Power Loss	-
Minimum Recommended Wire Size	-

About Voltage Drop

Voltage drop occurs when voltage decreases as current travels through a conductor due to resistance. Excessive voltage drop can cause:

This calculator uses the standard voltage drop formula:

Voltage Drop (V) = (2 × I × R × L) / 1000 (single phase)

Voltage Drop (V) = (1.732 × I × R × L) / 1000 (three phase)

Where:
I = Current (A)
R = Resistance (Ω/km)
L = One-way length (ft)

Important: This tool provides estimates only. Always consult local electrical codes and a licensed electrician for critical installations.

Voltage Drop Calculator