Calculate the correct wire gauge (AWG) for your electrical project based on amperage, voltage, and distance. Ensures safe operation and minimal voltage drop.
Undersized wire creates excessive resistance, causing heat buildup (fire hazard), voltage drop (equipment malfunction), and energy waste. Wire must be sized for both ampacity (current carrying capacity) and voltage drop.
Copper has better conductivity and is standard for branch circuits. Aluminum is cheaper and lighter but requires larger gauges for the same ampacity. Aluminum is common for service entrance and feeder cables. Special connectors are needed for aluminum.
Voltage drop is the reduction in voltage as electricity travels through wire. Long runs or undersized wire increase voltage drop, causing lights to dim, motors to run hot, and equipment to malfunction. Keep voltage drop under 3% for best performance.
Wire must always meet minimum ampacity requirements regardless of distance. Short runs may allow minimum gauge, but you can never go smaller than what the ampacity tables specify. For example, a 20A circuit requires minimum 12 AWG copper regardless of length.