Residential Wire Gauge Calculator

Determine the correct AWG wire size for any residential circuit : fast, free, and accurate.

Enter Circuit Details

The continuous ampere draw of the circuit load.

Distance from panel to the load (one way).

How It Works

This calculator determines the minimum AWG (American Wire Gauge) size needed for a residential circuit based on two independent criteria, then recommends the larger (safer) wire:

  1. Ampacity Check (NEC 310.15): The conductor must carry the load current continuously without overheating. NEC requires continuous loads to be derated to 80% of breaker rating. We compare your amperage against standard AWG ampacity tables (75°C column for residential use).
  2. Voltage Drop Check: Using the formula VD = (2 × K × I × L) / CM, where K is the resistivity constant (12.9 for copper, 21.2 for aluminum), I is current in amps, L is one-way length in feet, and CM is the wire's circular mil area. We find the smallest gauge that keeps voltage drop within your selected limit.

The final recommendation is the gauge that satisfies both constraints. Always verify your installation against local codes and the National Electrical Code (NEC).

Disclaimer: This tool is for estimation and educational purposes. Always consult a licensed electrician and local AHJ for final wire sizing decisions.