What wire gauge do I need for a 20 amp circuit?

A 20-amp circuit requires minimum 12 AWG copper wire (or 10 AWG aluminum). For runs over 75 feet, consider 10 AWG copper to keep voltage drop under 3%.

What wire gauge for a 30 amp circuit?

10 AWG copper wire is required for a 30-amp circuit. For long runs (over 50 feet), use 8 AWG to minimize voltage drop.

What is the NEC ampacity table?

NEC Table 310.15(B)(16) lists the maximum ampacity for conductors based on wire gauge, material (copper/aluminum), and temperature rating (60°C, 75°C, 90°C).

Can I use aluminum wire for home wiring?

Aluminum wire is acceptable for large-gauge feeders (6 AWG and larger) but is not recommended for 15 or 20-amp branch circuits due to connection issues.

What is voltage drop and why does it matter?

Voltage drop is the reduction in voltage over a wire run due to resistance. NEC recommends keeping voltage drop under 3% to ensure proper operation of devices at the end of the circuit.

Wire Gauge Calculator — AWG Size by Amps & Length

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Quick Answer

To find the correct wire gauge, look up your amperage in the NEC ampacity table (e.g., 20A needs minimum 12 AWG copper) and verify the voltage drop stays under 3% for the run length. This calculator cross-references both requirements and recommends upsizing when needed.

Use the Wire Gauge Calculator below to get instant results.

Wire Gauge Calculator

Enter your circuit details to find the recommended AWG wire gauge based on NEC ampacity tables.

Amperage (A): One-way Wire Length (ft): Voltage: Wire Material:

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Cite This Tool

Wire Gauge Calculator. (2026). Electrical Calculators Online. Retrieved from https://electricalcalcpro.com/wire-gauge-calculator/

Wire Gauge Calculator

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