Daily water intake calculator
Explore a rough daily water estimate based on body weight, exercise time and climate. The total is a rule-of-thumb calculation, not a prescribed amount to drink.
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This is a rough estimate of total water from food and drinks, not an amount you must drink. Needs vary with diet, activity, weather, medication and health.
Follow any fluid advice from your clinician, especially if you have been told to limit how much you drink.
How to use
- Enter weight. Choose kilograms or pounds. The estimate uses weight; the shared height field does not affect this result.
- Add exercise time and climate. Enter minutes of activity and choose Temperate, Warm or Hot or humid.
- Read the breakdown. For 70 kg, 30 minutes of exercise and Temperate, the calculation is 2.45 L from weight plus 0.40 L for activity: 2.85 L in total.
Questions
How is the number calculated?
The tool uses 35 ml per kilogram, adds 400 ml per 30 minutes of exercise, then adds 350 ml for Warm or 750 ml for Hot or humid. These are fixed assumptions, not measurements of fluid loss or a clinical guideline.
Is this extra water on top of food and other drinks?
No. Read it as a rough total-water estimate, including water from food and drinks, not an additional plain-water allowance. The calculator does not measure what you have already consumed or subtract it from the total.
Who should avoid using this as a daily target?
This simple adult estimate does not assess children, pregnancy, breastfeeding, illness, medication or conditions that affect fluid needs. It should not replace a clinician’s fluid instructions or be used to force a fixed intake.
How it works and sources
How this is calculated
The tool starts at 35 ml per kilogram of body weight, adds 400 ml per 30 minutes of exercise, then adds 350 ml for a warm climate or 750 ml for a hot one. These are rules of thumb, not an EFSA formula. For comparison, EFSA gives adult adequate intakes of 2.0 litres for women and 2.5 litres for men, counting both drinks and water in food, under moderate conditions.
What the calculation assumes
- The result is a rough adult estimate. It does not measure sweat loss or account for water in your meals.
- EFSA’s total-water figures include food and drinks. The amount supplied by food varies with your diet.
Where the result has limits
- The result is also displayed as glasses, but the tool does not clearly distinguish a drinking-water target from total water. Do not treat it as a required volume to drink in addition to food and other drinks.
- EFSA is cited for total-water guidance, not as evidence for the weight, exercise or climate adjustments used here. Those adjustments need their own source review.
- Needs differ in pregnancy, breastfeeding, illness and prolonged exercise. Follow any medical advice about fluid intake rather than this estimate.
- Drinking too much water quickly can be harmful. This calculation is not a replacement for an individual hydration plan.
Sources
- Scientific Opinion on Dietary Reference Values for water (adequate intake: 2.0 L/day women, 2.5 L/day men, total water) European Food Safety Authority
Sources last checked 30 July 2026.
These estimates are general information, not medical advice.
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