You often hear that you need to drink eight 8-ounce glasses of water each day. The Institute of Medicine's Food and Nutrition Board recommended that women actually need 91 ounces of water daily, and men need 125 ounces. You can get enough water each day by drinking water and other fluids like soup and drinks, along with lots of fruits and vegetables, which contain water. If you do something strenuous, like playing sports or running, you'll need extra water before, during, and after.