How much water an 11 year old girl should drink?

A good method to find out how much water you should drink, is to take your body weight and divide it by 2. Then, that number is how many ounces you're supposed to drink. For example, let's say you weigh 90 pounds. 90 divided by 2 would obviously be 45. So that means you should be drinking about 45 oz. each day.