So how much water do we actually need? Enough to replace the fluids you lose each day is determined by your size, your activity level, and the climate. A simple method of determining if you are getting enough (adequately hydrated) is the color of your urine (provided you are not mega-dosing on vitamins or taking certain medications). It should be lightly yellow. Dark yellow could indicate you need more water.
LifeTip: Eating foods with a high water content (fruits and vegetables) adds to your total liquid intake, and can reduce how much you drink.
Adapted from PositiveChoices.com