How much water should you drink in a day? It depends on your body size, how much you move and how hot it is. This calculator gives a personal estimate of your daily fluid needs, shown in liters, cups and glasses (or fluid ounces).
How the estimate works
It starts with about 33 milliliters of fluid per kilogram of body weight, which is about half an ounce per pound. It then adds roughly 350 milliliters (12 ounces) for every 30 minutes of exercise, and about 500 milliliters if you live or exercise in hot or humid conditions. The total is your suggested intake from all drinks.
This is consistent with reference values from the U.S. National Academies, which suggest about 2.7 liters of total water a day for women and about 3.7 liters for men, with roughly 20 percent coming from food.
What counts toward your total
- Water, sparkling water, tea, coffee and milk all count.
- Fruit, vegetables, soups and yogurt supply water as well.
- Alcohol does not hydrate well, and sugary drinks add calories without much benefit.
Signs you are drinking enough
A simple check is the color of your urine: pale straw yellow usually means you are well hydrated, while dark yellow or amber suggests you need more fluids. Thirst is also a reliable guide for most healthy adults. Read more in our full guide to how much water you really need each day.
Check with a professional if…
- You have heart, kidney or liver disease, or take medicine that affects fluids. You may have a fluid limit.
- You are constantly thirsty and urinating often, which can be a sign of diabetes.
- You are pregnant or breastfeeding and want a personal target.
Frequently asked questions
How much water should I drink a day?
Many healthy adults need about 2 to 3 liters of total fluid a day, including food. Use the estimate above and adjust for heat, exercise and illness.
Do I need to drink more when I exercise?
Yes. You lose fluid through sweat, so drink before, during and after longer workouts. The calculator adds about 350 ml per 30 minutes of exercise.
Does coffee count as water?
Yes. Moderate amounts of coffee and tea contribute to your fluid intake.
Can you drink too much water?
It is uncommon, but drinking far more than you need, especially during long endurance events, can dilute blood sodium. Let thirst guide you and avoid forcing large volumes.
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This calculator provides general estimates for healthy adults and is for information only. It is not medical advice and does not replace a conversation with a qualified healthcare professional. Read our disclaimer and editorial policy.