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Use this water intake calculator to estimate how much water to drink per day based on body weight, activity level, and climate. It gives a practical hydration target you can adjust for workouts, hot weather, sweat, thirst, and your normal routine.
Updated: May 8, 2026
Looking for a related estimate? Try Calorie Calculator or TDEE Calculator.
What you will get
Clear input, result, and explanation in one place
The result shows a practical hydration baseline that is easy to remember and adjust.
Snippet
This page helps you estimate a practical daily water target so you can compare routine hydration with your activity and climate. It is built for long-tail questions like how much water should I drink by weight, how much water should I drink when exercising, and whether a fixed 8-glass rule is enough.
When to use it
Use it when you want a baseline for daily water intake, when your activity changes, or when hot weather makes your usual routine feel less reliable.
Calculator
Inputs
Live updatesUse weight, activity, and climate to estimate a daily hydration baseline.
Result
The result shows a practical hydration baseline that is easy to remember and adjust.
Current estimate
2.8 L per day
This is a simple hydration baseline you can adjust for your routine and environment.
Supporting details
Daily water guidance
Most adults land somewhere around 2-3 litres a day, but the right amount changes with body weight, activity level, climate, sweat rate, and diet. A weight-based rule is often a better starting point than a fixed glass count because it adapts to the size of the person using it.
Example
If you weigh 70 kg, your daily water intake may fall around 2–2.5 litres depending on activity and environment.
Warning signs
Dark urine, fatigue, dry mouth, and headaches can be signs that you are under-hydrated. They are not a diagnosis, but they can help you notice when your routine needs a reset.
Exercise
Exercise, hot weather, outdoor work, fever, and heavy sweating can all increase fluid needs. Use the calculator result as your baseline, then add more fluid around workouts or heat exposure instead of forcing the same number every day.
Comparison
The “8 glasses rule” is not universal because hydration depends on body size, climate, and lifestyle. A simple calculator is usually more useful than a one-size-fits-all number.
Common questions
Many adults sit around 2–3 litres daily, but the best number depends on body size, activity, and climate.
It can contribute to fluid intake, but water is still the simplest way to meet a daily hydration target.
Yes. Very high intake can be a problem, so it is best to aim for a practical target rather than forcing water intake.
Body size influences the baseline, which is why weight is a useful part of the estimate.
Hydration helps support a routine, but water intake alone does not drive weight loss.
Usually yes. Exercise and sweating can raise fluid needs, especially in warm or hot conditions.
Helpful guide
Understand target heart rate zones, resting heart rate, calorie burn, VO2 max, and how to use the right fitness calculator next.
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