How much water should you drink each day? — a simple question with no easy answer. Just as you are unique, so are your water needs. And how much water you need depends on many factors, including your health status, how active you are and where you live.

Though no single formula fits all people, several guidelines are available to help you estimate how much to drink each day. Delve into your daily fluid needs to learn how your body uses water and what factors may increase — or decrease — your water requirements.

This isn't an easy question to answer. A healthy adult's daily fluid intake can vary widely. Most people drink fluid to quench thirst, to supply perceived water needs and "out of habit." At least three approaches estimate total fluid (water) needs for healthy, sedentary adults living in a temperate climate.

• Replacement approach. The average urine output for adults is 1.5 liters a day. You lose close to an additional liter of water a day through breathing, sweating and bowel movements. Food usually accounts for 20 percent of your fluid intake, so you if you consume 2 liters of water or other beverages a day (a little more than 8 cups), along with your normal diet, you can replace the lost fluids.
• Eight 8-ounce glasses of water a day. Another approach to water intake is the "8 x 8 rule" — drink eight 8-ounce glasses of water a day (about 1.9 liters). The rule could also be stated, "drink eight 8-ounce glasses of fluid a day," as all fluids count toward the daily total. Though this approach isn't supported by scientific evidence, many people use this basic rule as a guideline for how much water and other fluids to drink.
• Dietary recommendations. The Institute of Medicine recommends that men consume 3 liters (about 13 cups) of total beverages a day and women consume 2.2 liters (about 9 cups) of total beverages a day. These guidelines are based on national food surveys that assessed people's average fluid intakes.

You can choose any of these fluid intake approaches to gauge your fluid needs. But your current total fluid intake is probably OK if you drink enough water to quench your thirst, produce a colorless or slightly yellow normal amount of urine, and feel well.  Water: How much should you drink every day?