Daily Water Intake Calculator
The "eight glasses a day" rule was never based on much. What you actually need depends on how much of you there is, how much you sweat, and where you live — and an Indian summer changes that answer more than most calculators admit.
This one takes your weight, your activity level and your climate, and gives you a range rather than a single number, because that is how the science actually reads.
This is an estimate for healthy adults, not medical advice. If you are pregnant, breastfeeding, or managing a medical condition, speak to your doctor before acting on it.
How it works
We start from 30 to 35 ml of water per kilogram of body weight, which is the range Indian and European nutrition bodies converge on for healthy adults. We then add for activity, because you lose water through sweat and breath while you train, and again for hot or humid conditions.
(30 to 35 ml x your weight in kg) + activity + climate
A worked example
Someone weighing 72 kg who trains three to five days a week, in normal conditions: 30 x 72 = 2,160 ml to 35 x 72 = 2,520 ml, plus 500 ml for activity. That is roughly 2.7 to 3.0 litres a day. Move them to a hot, humid month and it becomes 3.2 to 3.5 litres.
What it cannot tell you
- Around a fifth of your daily water comes from food, so the number on your bottle does not have to hit this on its own.
- Kidney, heart and liver conditions change fluid needs significantly. If you have one, your doctor sets your number, not a calculator.
- Pregnancy and breastfeeding both raise requirements beyond what this estimates.
Frequently asked
- How much water should I drink a day in India?
- For most healthy adults, roughly 30 to 35 ml per kilogram of body weight, plus more for exercise and for hot or humid weather. For a 70 kg adult that is about 2.1 to 2.5 litres before any adjustment.
- Does tea, coffee or juice count?
- They contribute to your total fluid intake. Plain water is still the cleanest choice, and sugary drinks bring calories you probably did not intend to drink.
- Can I drink too much water?
- It is rare, but drinking a very large volume in a short time can dilute blood sodium, which is dangerous. Spread your intake through the day rather than front-loading it.
- How do I know if I am drinking enough?
- Pale straw-coloured urine is the simplest everyday signal. Dark urine, headaches, fatigue and poor concentration often point the other way.