Stevenski....
Good point.
18ga wire = 1.024mm = 24.5mm @ 1/24 scale
20ga wire = 0.813mm = 19.5mm @ 1/24 scale
24ga wire = 0.510mm = 12.25mm @ 1/24 scale
Again, hope that helps.
As far as a gauge, it is a measure of the thickness in some way or other.
Not sure exactly where it comes from.
But I just looked up the sizes for the gauges, and then scaled them.
-matt