Water Intake Calculator
Calculate daily water intake.
Input
Result
What is a Water Intake Calculator?
A Water Intake Calculator estimates how much fluid you should drink daily based on your body weight and activity level. Staying properly hydrated is essential for digestion, temperature regulation, and overall health.
How to calculate water intake manually (the formula)
A simple formula is 30 to 40 ml of water per kg of body weight. For a 72 kg person: 72 × 35 ml = 2520 ml or about 2.5 litres per day. Increase by 500 ml for intense exercise or hot weather.
Example calculation
A 65 kg woman with moderate activity: 65 × 35 = 2275 ml (about 2.3 litres) per day. If she exercises for an hour, add another 500 ml, bringing the total to about 2.8 litres.
Common mistakes
- Waiting until thirsty — Thirst is a late sign of dehydration. Sip water consistently throughout the day rather than drinking large amounts infrequently.
- Ignoring activity and climate — Exercise, heat, and humidity significantly increase water needs. Adjust your intake based on your environment and activity level.
- Over-relying on thirst alone — Older adults and athletes may have blunted thirst signals. Use urine color as a guide: pale yellow indicates good hydration.
Frequently asked questions
How much water should I drink per day?
A common recommendation is 3.7 litres for men and 2.7 litres for women from all beverages and foods. Individual needs vary based on activity, climate, and health.
How is daily water intake calculated?
Water intake is often calculated based on body weight. A general guideline is 30 to 40 ml per kg of body weight. Athletes and hot climates may require more.
Does other drinks count as water intake?
Yes, all fluids count toward your daily water intake including water, tea, coffee, milk, and juice. Even water-rich foods like fruits and soup contribute.
Can I drink too much water?
Yes, excessive water intake can lead to hyponatremia (low sodium levels). Stick to recommended amounts and listen to your thirst signals.
What are signs of dehydration?
Common signs include dark urine, dry mouth, headache, fatigue, and dizziness. Drink water regularly throughout the day to stay hydrated.