The Water Intake Calculator estimates how much water you should drink each day. Enter your weight, choose your activity level, and note whether you’re in a hot climate, and it gives your recommended daily intake in both litres and glasses.
Staying well hydrated supports energy, focus, digestion, and overall health. This is a general guide based on body weight and activity — everyone’s needs differ. The calculation runs entirely in your browser, so nothing you enter is stored.
How to use the water intake calculator
- Set your weight using the slider.
- Choose your activity level, from sedentary to very active.
- Tick the box if you live in or are spending time in a hot or humid climate.
- Read your recommended daily water intake in litres and glasses.
How much water do you really need?
A widely used rule of thumb is about 35 ml of water per kilogram of body weight, with more added for physical activity and hot weather. So a 70 kg adult needs roughly 2.4–2.5 litres a day at a light activity level, rising with exercise.
Remember that water from food, tea, coffee, and other drinks counts toward your total, so you don’t need to drink all of it as plain water. Thirst and the colour of your urine — pale straw is ideal — are good everyday guides.
Tips to stay hydrated
- Start the day with a glass of water and keep a bottle nearby.
- Drink more around exercise and in hot, humid weather.
- Fruits and vegetables with high water content add to your intake.
- People who are pregnant, breastfeeding, or unwell may need more — ask a doctor.
Frequently Asked Questions
How many litres of water should I drink a day?
It depends on your weight, activity, and climate. As a rough guide, about 35 ml per kg of body weight, plus more for exercise and heat. Enter your details above for a personal estimate.
Do tea, coffee, and food count toward my water intake?
Yes. Most drinks and many foods contribute to hydration, so you don’t need to consume the whole amount as plain water. The estimate here is your total daily fluid target.
Can I drink too much water?
In rare cases, drinking very large amounts in a short time can dilute your body’s sodium. For almost everyone, spreading normal amounts through the day is safe. If in doubt, ask a doctor.
Is this a substitute for medical advice?
No. This tool gives a general estimate. Individual needs vary with health conditions, medication, pregnancy, and more — consult a doctor for personalised guidance.