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I've always just accepted this but why is it that wire gauge goes down as wire size increases? Why not the other way which would make a bit more logical sense?

i.e. Why isn't it that 40 AWG = big wire, 0000 AWG = small wire.

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  • \$\begingroup\$ There is plenty of information on the topic out there. Here is one of first results: falconerelectronics.com/wire-gauge \$\endgroup\$ – Eugene Sh. Aug 22 '19 at 19:03
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    \$\begingroup\$ "This question does not show any research effort" \$\endgroup\$ – pipe Aug 22 '19 at 19:38
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    \$\begingroup\$ @C.Lange Today the minimum research effort usually means "google it and check the first link". When that doesn't help, you can ask here and show what exactly it is you don't understand from that answer. No need to make Stack Exchange into a copy of Wikipedia. \$\endgroup\$ – pipe Aug 22 '19 at 21:36
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    \$\begingroup\$ @pipe Gotcha. I thought the idea was to create a repository of Q&A questions. This was a question that had not been asked here so I thought it appropriate to add. Perhaps I've misunderstood the purpose of this site then. I'll keep that in mind -- thanks for the information! \$\endgroup\$ – C. Lange Aug 22 '19 at 21:58
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    \$\begingroup\$ It's easy, @Neil. The diameter is given by \$ D_{AWG}=0.005 \cdot 92^{\frac{36-AWG}{39} \ \text {inch} \$. Can't you do it in your head? \$\endgroup\$ – Transistor Aug 23 '19 at 15:14
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A seminal empirical definition of wire gauge was the number of times the wire had been passed through a draw plate. Each draw plate would reduce the diameter of the wire by about 10%, therefore the more it had been drawn (higher gauge) the thinner it would be.

Geometric approaches such as AWG define a ratio between wire sizes (AWG uses a ratio of 0.890526). Thus, a 31 gauge wire has a diameter 0.890526 that of a 30 gauge wire. This correlates roughly to the empirical definition.

It gets more complicated with stranded wires, but this explains why larger gauges mean smaller wires. (Shotgun shells work the same way.)

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  • \$\begingroup\$ AWG does mean American Wire Gauge, just to support your answer... plus1 :) \$\endgroup\$ – Solar Mike Aug 22 '19 at 19:15
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    \$\begingroup\$ Other examples are metal gauges. Higher gauges are thinner. Of course the same gauge numbers mean different thicknesses in mm for steel vs. galvanized steel vs. copper. 16 gauge steel is about 1.5mm vs. 1.29mm in copper or brass vs. 1.61mm in galvanized steel. Imperial drill bits also have one of the several size systems that follows an obsolete wire gauge. \$\endgroup\$ – Spehro Pefhany Aug 22 '19 at 20:37
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    \$\begingroup\$ @SpehroPefhany my feeler gauges have larger numbers as thicker: 5 thou is 5 thousandths of an inch, 35 thou is 35 thousandths of an inch and is seven times thicker... \$\endgroup\$ – Solar Mike Aug 23 '19 at 4:34
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    \$\begingroup\$ Shotgun gauge N, as I understand it, has the diameter of a lead ball weighing 1/N pound. \$\endgroup\$ – Anton Sherwood Aug 23 '19 at 6:23

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