Stay adequately hydrated. A simple formula from Dr. Sonja Petterson to calculate your baseline water requirement is Bodyweight (lbs) / 2 + 20% = oz/day For example, a 187 lb (85 kg) individual would have a baseline requirement of 112 oz per day. More water is needed according to daily activity. Bodyweight can be taken before and after training to measure water loss. Each pound lost represents 16 oz of water that must be replaced.