There are many different opinions on how much water a person should drink each day. The amount of water a person needs depends on many factors, including their age, health, activity level, and the climate they live in. Most health authorities recommend that adults drink eight 8-ounce glasses of water per day. This is equivalent to about 2 liters, or half a gallon. Some people may need more or less depending on the factors mentioned above. If you’re not sure how much water you should be drinking, talk to your doctor or a registered dietitian. They can help you determine how much water is right for you.