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Name: Tom F.
Status: student
Age: 16
Location: N/A 
Country: N/A
Date: 9/6/2004

I am doing an experiment at school and we are using nichrome wires of different swg thickness e.g. 22swg, 24swg....

As the swg goes up does the thickness of the wire decrease? Just what is 'swg'?


SWG stands for "Standard Wire Gauge". As the wire gauge number increases, the diameter of the wire decreases. Here is a website where you can see the wire diameters for each wire gauge number:


Todd Clark, Office of Science
U.S. Department of Energy

Hey Tom-

I thought it was "AWG". "American Wire Gauge".

But I suppose there might be an "SWG", meaning about the same thing. "Standard wire gauge" or "Stubbs wire gauge"? there were a bunch of them. Really antique units, a little bit newer than horse-shoes. 100+ years ago, "Gauge" usually meant "how many of those things can be stuffed into this here gauge?"

For wire, perhaps this gauge was a circular hole in a metal sheet.

So yes, higher gauge-numbers means smaller wire.

In the "awg" system, adding 3 units means half as much metal. Put another way, area decreases by two, diameter decreases by square root of two.

Of course, the available steps are almost always 2 units, (eg 22 to 24 awg) So you need to find a "wire gauge table" and make that data yours. Or just measure diameter with a micrometer, and measure resistance per meter with an ohmmeter and ruler. Or weigh a known length on a sensitive balance.

good luck with the experiment-

Jim Swenson PS- Europeans have graduated to less arcane units: "circular millimeters" of wire cross-sectional area. Almost the same as square millimeters, except a factor of pi/4. Sigh.


"swg" stands for Imperial Standard Wire Gauge, which is the British legal standard. Other common gauges are:

awg American Wire Gauge

B&S Brown & Sharpe

These are not rational or helpful units and it is probably better to specify the wire diameter in inches if you want to get the right wire. Millimeters would be even better (much better), but that is too much to hope for!

Gauge 1 has a diameter of 0.300 inches in swg and 0.289297 in awg or B&S.

Gauge 10 has a diameter of 0.1280 inches in swg and 0.1019 in awg or B&S.

And yes, as the gauge increases, the diameter of the wire decreases.

Best, Dick Plano.

AWG means American Wire Gauge and SWG means (British) Standard Wire Gauge.

In the AWG system, the diameter of the wire doubles when the AWG decreases by six. For example, 30 gauge is about 0.01" diameter, 24 gauge is about 0.02" diameter, 18 gauge is about 0.04" diameter, etc.

SWG seems to follow no discernable pattern.

Comparisons of AWG and SWG can be found in tables on the Internet.

Bob Erck

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