Don loves stuff like this so I will post it for his entertainment -- and anyone elses who may need it.
http://www.waterandwastewater.com/resources/capacity_calculators/
You mean I can forget everything I know about "Pi", squaring radii, and all that?
Sheesh, what's the world coming to? ;D ;D
But calculators tailored for the job are handy. :)
I had already calculated out the tank capacity on the tank I was quoting to do the repairs on -- 19000 gallons when I got lazy and thought I would Google it for calculators.
It, of course, confirmed that I was right. :) So keep the old brain working and just use these to check it. ;D