I've been advised by my mentor to drink 11 8oz. cups of water per day. I am 5'7" and weigh 187, and I am on a diet to lose weight, because I should not weigh this much! I usually gain weight during the winter months as one of my main modes of exercize is to go out walking, but who wants to do that when it is in the mid 30s Farinheight outside.
I stopped counting the glasses of water and doing the math, because I drink out of a 12 oz. glass, so I just try to be drinking all day and don't worry if I make my target exactly or not. I just figure if my inflow of water is pretty much constant throughout the day, I'll be OK.
One thing I did realize though is that I should get one of those sports bottles for water, so I don't spill it! Nothing like just barely missing one's calulator with a tipped glass, or worse yet, one's cell phone! So getting a bottle is on my TO DO List.