This site has a calc that is pretty cool...
<a href="http://www.aquasite.com/knowledge/calculator/calculator.shtml" target="_blank">http://www.aquasite.com/knowledge/calculator/calculator.shtml</a>
tw
This is the sand bed calculator I see most of the time:
Equation:
L x W x H x .0641 = lbs. of Sand needed
Where L = the length of the aquarium in inches, W = the width of the aquarium in inches, and H = the desired depth of sand in inches.
I just set up a 72 gallon bowfront. I used 125 lbs southdown and 40 lbs live sand for seed. The depth veries from 4-5 inches throughout the tank. HTH
Mini-Reefer