Proper hydration can help you feel and perform your best. However, exactly how much fluid you need each day depends on many factors including your gender, age, and weight, your environment, your health and your activity level. In addition, how much you need to drink each day is determined by your overall diet. The Institute of Medicine estimates that Americans get an average of 80% of their daily fluids from drinking water and other beverages and the remaining 20% from food. User this hydration calculator to estimate your daily hydration needs; including how much you need to drink each day.