lol..
The Yahoo search function works wonders...
I found the info at bobvila.com
http://www.bobvila.com/TipLibrary/Ta...od_Weight.html
- Plywood Weight
An easy way to estimate how much a stack of plywood will weigh is to figure about 25 lbs. per 1/4 in. of thickness. For example, one 4x8-ft. sheet of 1/4-in. plywood will weigh about 25 lbs., 1/2-in. about 50 lbs., and 3/4-in. about 75 lbs. This can help you decide how many trips you need to make to get a stack home, or whether you should have it delivered.