Wire Size, AWG and Funny Numbers

It amazes me how the smallest details can escape you.  Or, well, escape me.  Wire gauge seems simple enough, it’s a number that gets smaller as the wire gets bigger, right?  14 gauge wire is smaller than 12 gauge, and like that.  I’m running 4 gauge welding wire on my batteries and motor, and others are running 2 gauge.

So, the first thing is that if you’re a wire nerd, you refer to it as 4 AWG.  AWG refers to the American Wire Gauge standard, (also known as the Browne and Sharpe wire gauge) and it’s been in common use since the 1800s.

So, what threw me is that you see, for example 4 AWG, right?  Then you see numbers like 4/0 AWG.  You may guess that 4/0 AWG is just another way to say 4 AWG, you’d be wrong.  It goes like this.  4 AWG, 3 AWG, 2 AWG, 1 AWG, 0 AWG, 00 AWG, 000 AWG, 0000 AWG.  Another way to name this is with numbers, referring to the zeros.  That is, 0000 can also be called 4/0, (or, like, 4 zeros, or in wire-nerd-speak, “four-aught”).  Where a 4AWG wire is a little less than a 1/4″ thick, a 4/0 is about a half-inch thick.  Big difference.

Here’s a link to one of these clever little gages: General Tools 20 American Standard Wire Round Gage, and here’s a ton of wire-nerd info on the Wikipedia, and here’s a cool table of info for standard wire gauges that we use for EVs:

AWG Diameter Copper
resistance
NEC copper wire
ampacity with
60/75/90 °C
insulation (A)
Fusing Current
(copper)
in. mm (Ω/km)
(mΩ/m)
(Ω/kFT)
(mΩ/ft)
Preece
(~10s)
Onder-donk
(1s)
Onder-donk
(32ms)
0000 (4/0) .460 11.684 0.1608 0.04901 195 / 230 / 260 31 kA 173 kA
000 (3/0) .409 10.404 0.2028 0.06180 165 / 200 / 225 24.5 kA 137 kA
00 (2/0) .364 9.266 0.2557 0.07793 145 / 175 / 195 19.5 kA 109 kA
0 (1/0) .324 8.252 0.3224 0.09827 125 / 150 / 170 1.9 kA 15.5 kA 87 kA
1 .289 7.348 0.4066 0.1239 110 / 130 / 150 1.6 kA 12 kA 68 kA
2 .257 6.544 0.5127 0.1563 95 / 115 / 130 1.3 kA 9.7 kA 54 kA
3 .229 5.827 0.6465 0.1970 85 / 100 / 110 1.1 kA 7.7 kA 43 kA
4 .204 5.189 0.8152 0.2485 70 / 85 / 95 946 A 6.1 kA 34 kA
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3 responses to “Wire Size, AWG and Funny Numbers”

1. thanks!!! educating myself for a power inverter install on my 16 ram 2500 and would have surely mistaken 4/0 for #4.