What is the shortcut formula to find the weight of per square foot of the duct(regardless of gauge of duct)?

Thanks for the invite, I leave the answer to the experts

=SUM(((W+H)*2)*L)/12

W – width in inches, H – Height in Inches, L – Length in liner feet

weight of the square foot is depends up on sheet type and material.

Material and gauge  GI Sheet 24 G = 1.01 lbs/sqft (you can obtain it from material supplier or use standard size)

duct size 12" x 12" length 8ft

(12 + 12) x 2 x 8 / 12 = 48 x 8 / 12 = 384/12 = 32 Sqft

Weight of Duct = Total Sqft X Material Weight per Sqft = 32 x 1.01 = 32.32 lbs