AC Wire Size Calculator

Select the correct wire gauge (AWG) for your AC load and circuit distance

Circuit Parameters

Recommended Wire

Enter your circuit details and click Calculate.

AWG Reference Table (Copper, 60°C Column)

AWGAmpacityΩ / 1000ft (Cu)Ω / 1000ft (Al)

Frequently Asked Questions

How do I calculate wire size for an AC load?

Determine the load current (I = Watts ÷ Voltage for single-phase, or I = Watts ÷ (√3 × V × PF) for 3-phase). Pick an AWG that exceeds this current per NEC ampacity, then confirm voltage drop over the one-way distance stays under 3% for branch circuits or 5% total for feeders.

What wire size do I need for a 20 amp AC circuit 100 feet away?

For 20A at 120V single-phase, 100 ft: 12 AWG meets ampacity but causes ~6% drop. Use 10 AWG copper for ~3.9% drop, or 8 AWG for ~2.4% to stay safely under 3%.

What is the maximum voltage drop allowed for AC circuits?

NEC recommends 3% max for branch circuits and 5% for feeders, with a combined maximum of 5% from the service entrance to the farthest outlet.