Wire Size Calculator (AWG)

Calculate the proper wire gauge (AWG) for your electrical installation based on current and distance. This tool processes all data locally in your browser. No information is ever sent to any server. Completely free, no registration required.

How to Use the Wire Size Calculator (AWG)

1. Enter your input values above
2. Results update automatically
3. Copy or download the output

What is a Wire Size Calculator (AWG)?

A Wire Size Calculator determines the correct AWG (American Wire Gauge) wire size for electrical circuits based on amperage, voltage, distance (voltage drop), conductor material (copper or aluminum), and installation type. Choosing the right wire size is critical for safety: too small a wire overheats and causes fires; too large wastes money on unnecessary copper.

How Does It Work?

Enter circuit amperage, voltage (120V/240V), one-way wire distance, conductor material, and installation (conduit, cable, open air). The calculator determines: minimum AWG size per NEC ampacity tables, voltage drop percentage (recommended <3% for branch circuits, <5% total), and recommended upsized gauge if voltage drop exceeds limits.

Formula

NEC Ampacity: 14 AWG=15A, 12 AWG=20A, 10 AWG=30A, 8 AWG=40A, 6 AWG=55A\nVoltage Drop: Vd = 2 × K × I × L ÷ CM\nwhere K=resistivity (Cu=12.9, Al=21.2), I=amps, L=one-way feet, CM=circular mils\n% Drop = (Vd ÷ System Voltage) × 100%

Who Uses This Tool?

• Electricians sizing branch circuit wiring per NEC code
• DIY homeowners selecting correct wire for outlets and lighting
• Solar installers sizing wires for PV arrays
• Appliance installers determining wire gauge for high-amp equipment

Pro Tips

• NEC recommends <3% voltage drop for branch circuits and <5% total from service entrance. Voltage drop causes dim lights, motor wear, and efficiency loss
• Copper vs aluminum: aluminum needs 2 AWG sizes larger for the same current, but is lighter and cheaper. Use antioxidant paste on all aluminum connections
• Always size for the breaker protecting the wire — 14 AWG requires a 15A breaker max, 12 AWG = 20A max. The breaker protects the wire, not the device

Frequently Asked Questions about Wire Size Calculator (AWG)

Can I use 14 AWG for a 20-amp circuit?

No. NEC requires minimum 12 AWG for 20A circuits. Using 14 AWG on a 20A breaker risks overheating before the breaker trips — a fire hazard.

How far can I run 12 AWG wire?

At 20A, 120V: ~50 feet to stay under 3% voltage drop. At 100+ feet, voltage drop exceeds 5%. Upsize to 10 AWG or use 240V circuits for longer runs.

Free online Wire Size Calculator (AWG) — no signup, 100% client-side processing. All data stays in your browser.