thickness of different gauge sheetmetal.

[Mike Lee - Team Banana Racing <mikel@ichips.intel.com>]

A very basic question I'm sure, but they say the dumbest question
is the one that isn't asked.....

What is the correlation between the thickness of a piece of sheetmetal
and it's gauge?  I know the gauge is used as a measurement, and is
inverse to the thickness (i.e the higher the gauge number, the thinner
it is), but what is the actual correlation?  Or, what is the formula
for determining that #16 is .xxx" thick, and #22 is .xxx" thick?  Or
is there a table that I must memorize?

Thanks!
Mike