Estimate how much water to drink each day from your weight and activity.
Calculated locally in your browser.
How much water should you drink each day?
A general daily target is base ≈ weight(kg) × 0.033 litres, plus about 0.35 litres for every 30 minutes of exercise. So a 70 kg person exercising 30 minutes a day needs roughly 2.66 litres. This is a guide only; you also get water from food, and needs rise in heat, illness or pregnancy.
Understanding your result
This is a general guide. You also get water from food and other drinks, and needs rise in heat, illness or pregnancy.
Formula and method
Base ≈ weight(kg) × 0.033 litres, plus about 0.35 litres for every 30 minutes of exercise.
Assumptions and limitations
This is a general guide, not medical advice, and individual needs vary. It does not replace the water you get from food and other drinks, and requirements rise in hot weather, illness, pregnancy or intense activity. Some conditions affect fluid needs, so speak to a qualified professional if you have specific health concerns.
Worked example
A 70 kg person who exercises 30 minutes a day needs about 2.66 litres of water.
How to use this tool
- Enter your weight.
- Add your daily exercise minutes.
- Press Calculate.
About the Water Intake Calculator
The Water Intake Calculator estimates a daily water target from your body weight, with extra added for exercise.
Who should use this tool
Anyone wanting a general daily water target based on their body weight and exercise, as a simple reminder to stay hydrated. Useful for building a rough hydration goal, though individual needs shift with heat, activity, illness and other factors the estimate cannot fully capture.
Benefits
- Estimates a daily water target from weight and exercise
- Adds an allowance for time spent exercising
- Offers a simple baseline to build hydration habits
- Usable straight from the browser with zero setup
Practical use cases
- Setting a rough daily hydration goal
- Adjusting your target for exercise days
- Building a habit of drinking through the day
- Comparing your intake against a general baseline
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Frequently asked questions
Is 8 glasses a day right?
It’s a rough rule. Actual needs depend on your size, activity and climate — this calculator personalises the estimate.
Does this target include water from food and drinks?
The estimate focuses on water you drink, but in practice you also get fluid from food and other beverages, which contribute to your overall intake. That means your total hydration can be higher than the figure alone suggests. Treat the number as a general drinking-water guide rather than your entire fluid requirement.
When should I drink more than the estimate?
Needs rise in hot or humid conditions, during and after intense exercise, and in situations such as illness or pregnancy. The tool adds an allowance for exercise, but it cannot account for every factor. Listen to thirst, watch for signs of dehydration, and seek professional guidance for specific health concerns.