Water Intake Calculator
Find your daily hydration target in ounces, cups, and liters.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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This calculator estimates your daily water needs using the standard body-weight formula with adjustments for exercise and individual circumstances.
- Enter your weight. Select lbs or kg and type your current body weight. The base calculation uses weight in pounds divided by 2 to get the daily ounce target, which is one of the most widely cited clinical guidelines.
- Add exercise time. For every 30 minutes of moderate-intensity exercise, an additional 12 oz is added to replace sweat loss. Enter your average daily exercise duration in minutes.
- Check any applicable boxes. Hot climates and high heat exposure add 8 oz. Pregnancy and breastfeeding each add 8 oz per the Institute of Medicine guidelines.
- Read your results. Results appear in four units: fluid ounces, milliliters, 8-oz cups, and liters.
About Daily Water Intake
The body requires water for virtually every physiological process: nutrient transport, temperature regulation, joint lubrication, waste removal, and cellular function. Mild dehydration of just 1 to 2 percent of body weight can impair cognitive performance and physical endurance.
The "eight 8-oz glasses per day" rule (64 oz) is a common shorthand but does not account for body size. Larger people need more water. The weight-based formula used here provides a more personalized starting point. Note that total fluid intake includes water from food (roughly 20 percent of daily intake for most people) and other beverages. This calculator estimates water you should actively drink, consistent with general clinical guidance.
Frequently Asked Questions
How much water should I drink per day?
A common clinical guideline is to drink half your body weight in pounds as ounces of water per day. For a 160-pound person that is 80 oz, or about 10 cups. Add 12 oz for every 30 minutes of exercise. The National Academies suggest 3.7 liters total fluid per day for men and 2.7 liters for women, including water from food. Individual needs vary based on activity, climate, and health status.
Does exercise increase water needs?
Yes, significantly. During moderate exercise you can lose 0.5 to 1 liter of sweat per hour. The American College of Sports Medicine recommends drinking about 500 ml before exercise, 150 to 250 ml every 15 to 20 minutes during exercise, and enough afterward to replace sweat losses. This calculator adds 12 oz per 30 minutes of exercise as a practical approximation for daily planning.
Can you drink too much water?
Yes, but it is uncommon in everyday situations. Drinking far more water than your kidneys can process (more than about 1 liter per hour) can dilute blood sodium, causing hyponatremia. This is most often seen in endurance athletes who over-hydrate during long events. For most people following the guidelines in this calculator, over-hydration is not a concern. Your kidneys regulate water balance efficiently across a wide range of intake.
Does coffee or tea count toward my water intake?
Yes. Despite the common belief that caffeine is strongly dehydrating, research shows that moderate caffeine consumption (up to about 400 mg per day, or roughly 4 cups of coffee) does not cause net fluid loss in people who consume caffeine regularly. Tea, coffee, and most other beverages contribute to your daily fluid intake. Plain water is still the best choice for hydration since it contains no calories, acids, or other compounds, but caffeinated beverages do count.