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.
In beta. This lesson was written for Hone and has not yet been checked by a licensed electrician. Practice material, not professional advice. What that means.
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.