Wire Gauge Calculator
Find the right wire gauge for your circuit based on current and distance.
Results
Choosing the right wire gauge prevents voltage drop, overheating and fire hazards. Wire that is too thin for the current and distance causes excessive resistance and heat. This calculator uses the NEC 3% voltage drop guideline to recommend the minimum safe wire gauge for your circuit. Always round up to the next larger gauge for safety.
Explore all our electrical engineering calculator tools, or browse the full cooking hub.
Frequently asked questions
For a 20A circuit at 120V over 50 feet, you need at least 10 AWG wire to keep voltage drop under 3%. Shorter runs can use 12 AWG per NEC ampacity tables.
Longer runs need thicker wire. A 20A circuit at 50 feet needs 10 AWG, but at 100 feet it needs 8 AWG. Voltage drop doubles with distance.
The NEC recommends no more than 3% voltage drop for branch circuits and 5% total including the feeder. For a 120V circuit, 3% is 3.6 volts.
240V circuits need thinner wire for the same power because current is halved. A 4800W load draws 40A at 120V but only 20A at 240V, halving the wire size requirement.
Aluminum wire needs to be about 2 AWG sizes larger than copper for the same ampacity. 10 AWG copper is equivalent to roughly 8 AWG aluminum.