About the Water Intake Calculator
How much water should you actually drink? Get a personalized daily target based on your body weight and exercise time, shown in liters, fluid ounces, and cups.
Your weight and activity details stay on your device. Health figures are exactly the sort of data that should not be sitting in a stranger's database, so this tool never sends them anywhere.
Results are estimates for general information only and are not medical advice. Talk to a healthcare professional before making significant changes to your diet or exercise.
How to use it
- Enter your body weight.
- Add your daily activity level and exercise duration.
- Read your estimated daily fluid target.
Where the number comes from
A widely used starting point is roughly 30–40 ml of fluid per kilogram of body weight per day, adjusted upward for exercise, heat and altitude.
This is an estimate, not a prescription. Kidney function, medication, pregnancy and climate all shift the real requirement, and some medical conditions require deliberately restricting fluid.
A worked example
A 70 kg adult at 35 ml/kg needs about 2.5 litres a day.
Add a 45-minute workout, which typically costs 500 ml or more in sweat, and the target rises to roughly 3.0 litres.
Food contributes too — fruit, vegetables and soup can supply 20% of daily fluid, so the amount you actually need to drink is usually lower than the total figure.
Common mistakes
- Treating the number as a hard target rather than a rough guide. Thirst and urine color are better day-to-day signals.
- Assuming coffee and tea do not count. At normal intakes they contribute to hydration despite being mild diuretics.
- Drinking very large volumes rapidly during endurance events, which can dangerously dilute blood sodium.
Questions people ask
Do coffee and tea count toward the total?
Yes. The diuretic effect of caffeine at ordinary intakes is small and does not offset the fluid consumed.
How do I tell if I am drinking enough?
Pale straw-colored urine and an absence of persistent thirst are the practical everyday indicators.
Is it possible to drink too much water?
Yes, though it is uncommon. Consuming very large volumes in a short period can cause hyponatraemia, a serious drop in blood sodium. This tool is general information, not medical advice.