I still don't see the simple relation for the B&S gauge unit.
There’s no relationship between the various gauge systems.
There’s really not a very good relationship between gauge #s in
most systems relative to metal sizes used today. For my money,
the various gauge systems are a good example of ‘not invented
here’; everybody tried to use his own. The best bet is to ‘go
with the flow’. Order yourself a B&S gauge (about $15.00) from
one of the US tool suppliers; then you’ll have a US standard
against which to measure non-ferrous sheet & wire.
A lot of industries in the US are getting away from using the
various gau ge systems & going to decimal numbers when
specifying sheet & wire thicknes s e.g., .015 in. .125 in etc.
Now, if we could just get them to go metric!