how many ounces of water per day body weight
If you are training regularly, you will probably need between one half and one whole ounce of water (or other fluids) for each pound of body weight per day. For example, if you weigh 150 pounds, your approximate water requirement will be between 75 and 150 ounces each day.
At the International Sports Medicine Institute, we have a formula for daily water intake: 1/2 ounce per pound of body weight if you're not active (that's ten eight-ounce glasses if you weigh 160 pounds), and 2/3 ounce per pound if you're athletic (13 to 14 glasses a day, at the same weight).