"Jim Wilkins" wrote in message
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http://en.wikipedia.org/wiki/Sheet_metal

Steel a foot square by an inch thick weighs 40 lbs for figurin' purposes,
so 18 Ga which is nearly 1/20" thick should weigh 2 lbs per square foot.

jsw

This one gives the weight for gauges:
http://www.engineeringtoolbox.com/ga...eet-d_915.html

Notice that the thicknesses were chosen for their convenient fractional
weights in lbs / sq foot.

jsw