Fluids are needed for many body functions, including helping to move waste material from the body, regulating body temperature and carrying nutrients to the body's cells. According to Clemson State University, on average, a healthy adult needs one quart of water for every 50 lbs. of body weight. The U.S. Geological Survey states that water makes up approximately 60 percent of the human body, 70 percent of the brain, 90 percent of the lungs, 75 percent of lean muscle tissue, 10 percent of body fat, 22 percent of bones and 83 percent of blood.
Measure your current weight using a scale.
Determine how many quarts of water you need based on your body weight by dividing your weight in pounds by 50. This will give you the average amount of water you need to ingest per day. For example, an individual who weighs 120 pounds should divide her weight by 50. This individual needs to ingest 2.4 quarts of fluid per day.
Convert your water intake from quarts to cups. One cup equals 0.25 quarts. Divide your daily fluid intake in quarts by 0.25. Using the same example of the 120 pound individual from the previous step, 2.4 quarts of water divided by 0.25 equals 9.6 cups of water.
If you are exercising, ill, in a hot environment, or pregnant or breast-feeding, increase your intake of water.