The basic guideline is 8-12 8 oz glasses of water per day, though it varies based on many factors. Weight, specific health issues, activity level, personal preferences, etc. I say aim for that and see how you feel. I notice that on days where work is super hectic, I drink less, and I can totally tell because I can feel the dehydration in my body. I do my best now but the physical location of my water has to be away from my work (medical) areas so I don't have water right by my side, like I do everywhere else!