Water is your body’s principal chemical component and makes up approximately about 60 percent of your body weight. Every system in your body depends on water, and Its important to keep it hydrated. But where does the “eight, 8 oz glasses a day” rule come from? The Institute of Medicine determined that an adequate intake for men is roughly about 13 cups (3 liters) of total beverages a day, and about 9 cups (2.2 liters) for women. Although the “8 glasses a day” rule (1.9 liters) isn’t supported by hard evidence, but it isn’t that different from the Institute of Medicine recommendations, and it remains popular because it’s easy to remember!