Water Intake Calculator
Calculate your daily water intake based on your weight, activity level, and climate. Get results in litres and glasses.
Daily water intake
2.8 L
2800 ml · 11 glasses
1 glass = 250 ml
Individual needs vary. Increase intake if you sweat heavily, are pregnant, or breastfeeding.
How to Use
- 1
Enter your weight
Enter your body weight in kg or lbs.
- 2
Set activity and climate
Select your activity level and the climate you live or work in.
- 3
See your daily target
Your recommended daily water intake is shown in litres, ml, and number of glasses.
How It Works
This calculator estimates daily water intake based on body weight, activity level, and climate, giving results in both litres and standard glasses.
The base calculation
The baseline is roughly 35ml of water per kg of body weight per day. Exercise adds extra requirement on top of this baseline (since sweat increases fluid loss), and hot or humid climates add further still, since higher ambient temperature also increases fluid loss through perspiration even without exercise.
What counts toward hydration
Plain water is the most direct contributor, but herbal tea and water-rich foods (fruits, vegetables, soups) also count meaningfully toward daily hydration. Caffeinated drinks like coffee and regular tea have a mild diuretic effect, so they contribute somewhat less per volume than plain water, though the effect is smaller than commonly believed for moderate consumption.
Examples
Base calculation for a sedentary adult
A 70 kg adult with a sedentary lifestyle in a moderate climate: 70 × 35ml = 2,450ml ≈ 2.45 litres/day, or about 10 standard 250ml glasses.
Adjusted for exercise and hot climate
The same 70 kg person who exercises regularly and lives in a hot climate would see a meaningfully higher recommended intake, since both factors add to the baseline requirement independently.
Common Use Cases
- Setting a personalized daily water intake target based on your actual weight, activity, and climate
- Understanding how exercise or hot weather increases hydration needs above a generic "8 glasses a day" rule of thumb
- Tracking hydration goals alongside a fitness or health routine
Tips
- The commonly cited "8 glasses a day" is a rough generic guideline — actual needs vary significantly by body weight, activity level, and climate, which is exactly why a personalized calculation gives a more useful target than a one-size-fits-all number.
- Thirst itself is a reasonably reliable hydration signal for most healthy adults in normal conditions — use the calculated number as a target to aim for, not as a rigid requirement to hit exactly every single day.
Frequently Asked Questions
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