Lessons · Electrical · wire sizes (AWG)
Wire sizes: the smaller the number, the bigger the wire
American Wire Gauge counts down as the wire gets thicker: 14 AWG is small, 6 AWG is big, and 1/0, 2/0 and up are bigger still. Every three gauge steps roughly doubles the copper; ten steps is ten times the area, measured in circular mils.
Hone is a place to practise a career, one idea a day. This is one of its lessons, written out in full and free to read without an account.
What it is for
A supply house asks 'twelve or ten' and the answer decides whether the wire can carry the load, whether it fits the breaker's terminal and whether the conduit is legal. Reading a cable jacket and knowing instantly which is thicker is a skill you use every single day.
How to think about it
Say the sizes in order out loud until it is automatic: 14, 12, 10, 8, 6, 4, 3, 2, 1, 1/0, 2/0, 3/0, 4/0. For the area, square the diameter in mils (thousandths of an inch) to get circular mils, or take a size from the table and double it for every three gauge steps down.
Worked example
14 AWG: 0.0641 in = 64.1 mils; 64.1 × 64.1 = 4110 circular milsDiameter in mils, squared. The table value.
12 AWG = 6530 circular mils; 10 AWG = 10380 circular mils; 8 AWG = 16510 circular mils; 6 AWG = 26240 circular milsThe four sizes a house is wired with. Memorise these; you will use them in every voltage-drop calculation.
12 AWG is about 6530 / 4110 = 1.6 times the copper of 14 AWGTwo gauge steps, about 1.6 times. Three steps, about double: 14 to 11.
4 AWG: 41740 circular mils; ten steps down from 14 AWG, about 10 times 4110The ten-steps rule. 41740 / 4110 = 10.2, close enough to plan with.
Your turn
8 AWG has a diameter of 128.5 mils. Write the line that gives its area.
128.5 × = 16512 circular mils
Solve one, graded on the server
The trap
Reading 1/0 as one over zero and putting it below 1 AWG. 1/0 (one-aught) is one size bigger than 1 AWG, and 4/0 is the biggest of the aughts. The numbers count down to 1, then the aughts count up.