Everyone needs eight glasses of water a day.
That’s like saying everyone needs to eat 11,700 kilojoules a day. (They don’t.) Depending on body weight, activity level and temperature, your daily fluid needs can range from as little as 1.8 litres to more than 5.6 litres per day. On days when you don’t exercise, assess your pee. Your urine should look more like lemonade than water or apple juice. Dark urine often reflects dehydration. On days when you work out, weigh yourself pre- and post-exercise. For every halfkilogram of weight you lost, you’ll need to drink 2½ to 3 cups of fluid to restore balance.