Water Intake Calculator
The eight glasses rule was never based on anything. Intake scales with your size, how much you sweat and how hot it is, so this starts from those.
How the math works
Daily water = (body weight in pounds x 0.5 oz + 12 oz per 30 minutes of exercise) x a climate factor of 1 to 1.25. One cup is 8 oz and a gallon is 128 oz. Roughly 20 percent of daily fluid intake normally comes from food.
Common questions
- How much water should I drink a day?
- For most adults somewhere between 80 and 120 oz of total fluid, scaling with size and sweat. The figure above is a starting point, and urine color is a better daily check than any number: pale straw is right.
- Do coffee and tea count?
- Yes. The idea that caffeine dehydrates you does not hold up at normal intakes. A cup of coffee is a net fluid gain, and so is tea, juice and soda, whatever else may be wrong with the last one.
- Can you drink too much water?
- Yes, though it is rare. Drinking several liters quickly can dilute blood sodium, which is dangerous. Endurance athletes are the usual case, and it is why sports drinks carry electrolytes at all.