Water Intake Calculator
Work out how much water to drink each day based on your weight, exercise, weather and whether you are pregnant or breastfeeding.
If you have kidney, heart or liver problems, or take medicine that affects fluid, ask your doctor how much to drink. Thirst and pale yellow urine are good everyday signs that you are drinking enough.
How much water do you need?
A common starting point for healthy adults is around 30 to 35 ml of water per kilogram of body weight each day. The calculator uses 33 ml per kg, then adds extra for activity and conditions that make you lose more water.
- Exercise: about 350 ml for every 30 minutes of activity that makes you sweat.
- Hot or humid weather: about 500 ml extra, or 750 ml in extreme heat.
- Pregnancy: about 300 ml extra a day.
- Breastfeeding: about 700 ml extra a day.
For example, a 70 kg adult who exercises for 30 minutes on a hot day needs about 2.3 + 0.4 + 0.5 = 3.2 litres.
Does all of it have to be plain water?
No. Milk, tea, juice and other drinks count, and food such as fruit, vegetables, soups and rice provides around 20% of daily water. Water is still the best everyday choice because it has no sugar or calories.
Signs you are drinking enough
- You rarely feel thirsty.
- Your urine is pale yellow.
- You do not get headaches or feel tired from dehydration.
Dark urine, dizziness and a dry mouth are early signs of dehydration, especially in hot weather.
Can you drink too much?
Yes, although it is rare. Drinking very large amounts in a short time can lower blood sodium. Spread your water across the day rather than drinking it all at once. People with kidney, heart or liver conditions should follow their doctor’s advice on fluids.
Water Intake FAQs
Answers about daily water needs.
How many glasses of water should I drink a day?+
Many adults need about 8 to 12 glasses of 250 ml, depending on weight, activity and weather. The calculator gives a personal estimate.
Is 2 litres a day enough?+
It is a good minimum for many adults, but larger people, active people and anyone in hot weather usually need more.
Do tea and coffee count?+
Yes. Moderate amounts of tea and coffee count towards your daily fluid, although water is the healthiest choice.
How much water should I drink when exercising?+
Roughly 350 ml for every 30 minutes of activity, more in hot weather or if you sweat heavily. Sip before, during and after exercise.
Is my data saved?+
No. Everything is calculated in your browser and nothing is sent to our servers.
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