The Real Problem This Solves
The "8 glasses a day" rule is a myth that ignores your body weight and activity. Some people need far more, others less.
Under-hydration quietly drains energy and focus. This calculator gives you a personalised daily target.
How Your Water Need Is Estimated
A common guideline is about 35 ml of water per kg of body weight, with extra added for exercise. Hot weather, illness, and pregnancy raise the need further.
Example: Rahul weighs 70 kg and exercises 30 minutes daily. His base need is 2.45 litres, plus ~350 ml for exercise, totalling about 2.8 litres a day, or roughly 11 glasses.
| Body Weight | Light Activity | Daily Need |
|---|---|---|
| 50 kg | 30 min | ~2.1 litres |
| 70 kg | 30 min | ~2.8 litres |
| 90 kg | 30 min | ~3.5 litres |
Frequently Asked Questions
How much water should I drink a day?
Around 35 ml per kg of body weight is a good baseline, increased for exercise and hot weather. The calculator personalises this from your inputs.
Do tea, coffee and food count?
Yes, most fluids and water-rich foods contribute to hydration, though plain water is the healthiest main source. Very caffeinated drinks have a mild diuretic effect.
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Got your hydration target?
Hydration supports your fitness goals. Pair it with the right calorie intake using our Calorie (TDEE) Calculator.
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