Choosing between 12 AWG, 10 AWG, 8 AWG, 6 AWG, and 4 AWG is really about balancing current, distance, and voltage drop . The simple rule is this: the smaller the AWG number, the thicker the wire . That means 4 AWG is much larger than 12 AWG, carries more current, has lower resistance, and performs better on longer runs. For example, standard AWG charts show that 12 AWG copper has a cross-sectional area of about 3.31 mm² , while 4 AWG copper is about 21.15 mm² . Ampacity chart