Wire Gauge (AWG) Calculator

Calculate the minimum safe wire thickness to prevent voltage drop and dangerous heat.

System Voltage
Current / Amp Draw 20 A
One-Way Cable Length 15 ft
Acceptable Voltage Drop
Wire Material
Recommended Minimum
10 AWG
EXCEEDS LIMITS
0.00 V Actual Voltage Drop
0.0% Percent Drop

Why Wire Gauge Matters

In the American Wire Gauge (AWG) system, the numbers work backward: the smaller the number, the thicker the wire. Choosing the correct size requires satisfying two distinct physics rules:

  • Ampacity (Heat Limits): Pushing high current through a thin wire causes immense friction. The wire acts like a toaster heating element and can easily melt its insulation and cause a fire. The calculator cross-references the current against safe NEC ampacity limits.
  • Voltage Drop: Wire has natural electrical resistance. The longer the wire, the more voltage is lost as heat before it reaches your device. If a 12V battery drops 2 Volts over a 50-foot run, the device only receives 10V and may malfunction. To fix this, you must use a thicker wire to reduce resistance over distance.
  • Material: Copper is an excellent conductor. Aluminum is cheaper and lighter, but has higher resistance (Specific Resistance K = 21.2 vs Copper's 12.9). Therefore, Aluminum requires a significantly thicker gauge to carry the same load.
Theoretical Disclaimer: This tool calculates minimum wire size based on theoretical specific resistance and simplified ampacity tables. In real-world commercial or residential applications, the National Electrical Code (NEC) dictates sizes based on insulation temperature ratings (e.g., THHN vs Romex), ambient temperature, and whether wires are bundled in a conduit. Always consult a licensed electrician for building codes.