brad diameter vs "gauge"?

[Stephen Tashiro]

How is the diameter of a brad nail found if the "gauge" of the brad is given?

[Jim McFarland]

This calculator seems accurate for the 23ga and 18ga I checked:

http://www.66pacific.com/calculators/wire_calc.aspx

Edit to add: Not sure how you want to use the actual diameters -- 18 ga brad I have is actually more rectangular than round -- neither dimension matched the calculator exactly.

[Jeff Bratt]

Here a wire gauge chart... http://cattlecorner.com/conversions/wiregauge.htm
The numbers match with another reference I've got.