Water Intake Calculator
Estimate how much water to drink a day from your weight and exercise, in metric or imperial — free and private, right in your browser.
Report a problemThis is a general estimate, not medical advice. Your real needs change with climate, health, pregnancy and how active you are — food and other drinks count too. Ask a health professional for guidance about your own hydration.
How to use
- Pick metric (kilograms) or imperial (pounds) and type your body weight.
- Type how many minutes you exercise on a typical day. Leave it at 0 if you are resting.
- Read your suggested daily water target. It updates live as you type, in litres, cups and US fluid ounces.
FAQ
How is my daily water target worked out?
We start from your body weight: about 33 millilitres of water for every kilogram. Then we add roughly 350 millilitres for each 30 minutes of exercise, since you lose extra fluid when you sweat. The total is shown in litres, and also as cups (250 ml each) and US fluid ounces so you can use whichever measure suits your bottle or glass. It is a simple, popular rule of thumb — handy as a starting goal rather than an exact prescription.
Is anything I type sent to a server?
No. Your weight and exercise minutes are used for plain arithmetic right in your browser — nothing is uploaded or stored. The calculator works offline and keeps your numbers private.
Is this medical advice?
No, it is only an estimate. How much water you actually need depends on the weather, your health, any medication, pregnancy and the food and drinks you already have. Use this as a friendly guide, listen to your thirst, and talk to a doctor if you have a condition that affects your fluid balance.