Electrical Wire Size Calculator
Determine the correct AWG wire gauge for your electrical circuit. This calculator uses NEC voltage drop guidelines (max 3%) to recommend the proper wire size for copper or aluminum conductors at 120V or 240V.
Enter Your Circuit Details
Full Breakdown
Amperage
Voltage
Distance
Material
Recommended Gauge
Voltage Drop
Voltage Drop %
Wire Sizing Detail
How to Use This Calculator
- Enter the amperage of your circuit (check your breaker or appliance rating).
- Enter the one-way distance from the panel to the load in feet.
- Select your voltage (120V for most household circuits, 240V for dryers/ranges).
- Choose copper or aluminum wire.
- Click "Calculate Wire Size" to see the recommended AWG gauge.
The Formula
Wire sizing uses the NEC voltage drop method:
Required Circular Mils = (2 × Distance × K × Amps) ÷ Max Voltage Drop
Where K is the resistivity constant (10.4 for copper, 17.0 for aluminum), and maximum voltage drop is 3% of supply voltage per NEC recommendation.
Voltage Drop = (2 × Distance × K × Amps) ÷ Wire Circular Mils
The calculator selects the smallest standard AWG gauge that meets the circular mil requirement.