How much water you need
A common guideline bases daily water intake on body weight, then adds more for exercise. This calculator estimates a sensible daily target in litres from your weight and activity. It is a starting point; thirst, climate and health all matter too.
How it works
It uses roughly 35 ml of water per kilogram of body weight as a baseline, with extra added for exercise. Food and other drinks also count toward your total fluid, so you rarely need to drink the whole figure as plain water.
Worked example
A 70 kg person with no added exercise has a baseline of about 2.45 litres a day. An intense workout adds several hundred millilitres on top.
Frequently asked questions
How much water should I drink per day?
A common guide is about 35 ml per kg of body weight, so around 2.5 litres for a 70 kg person, plus more for exercise and hot weather. Food and drinks count.
Does coffee or tea count?
Yes, most fluids contribute to your total, including tea and coffee. Plain water is still the simplest way to top up.
Can I drink too much water?
Rarely, but drinking extreme amounts quickly can be harmful. Spread intake through the day and drink to thirst plus this target.
Is 8 glasses a day a rule?
It is a rough rule of thumb. Bodyweight-based targets like this one are more personalised.