How much water should I drink a day?

Roughly about 30 ml per kilogram of weight: at 70 kg, about 2.1 litres. Needs rise in heat and with exercise. All fluids count — including tea, soups and juicy foods — not just plain water.

Does everyone really need 8 glasses?

No, that’s a simplification. Needs are individual and depend on weight, activity and climate. The calculator gives a personal guide in litres and glasses for you.

Do tea and coffee count?

Yes. Tea, coffee, soups, milk, and juicy vegetables and fruit provide water and count toward the daily total. The idea that coffee “dehydrates” is a myth — in moderation it also contributes to fluid balance.

How do I know I’m drinking enough?

A simple guide is urine colour: pale yellow means enough, dark means you should drink more. Go by thirst too; there’s no need to force water beyond the norm.

Can you drink too much water?

Yes, in rare cases excess water is dangerous (hyponatremia), especially with kidney or heart disease. That’s why in those conditions a doctor sets the amount, not a general calculator.

How much water to drink a day

Enter your weight — the calculator estimates daily water needs at about 30 ml per kilogram and shows it in litres and glasses. Add exercise and a hot climate to refine it, and mark pregnancy or breastfeeding if relevant.

Calculate daily water intake

Enter your weight — the result appears instantly.

Daily water guidelines

All fluids count: water, tea, soups, juicy fruit. This is a guide for healthy adults; with kidney or heart disease your doctor sets the amount.

Situation	Adjustment
Base	≈ 30 ml per 1 kg
One hour of exercise	+ ~500 ml
Hot weather	+ ~15%
Pregnancy	+ ~300 ml
Breastfeeding	+ ~700 ml

How much water you need a day

There’s no universal “8 glasses for everyone” — needs depend on weight, activity and climate. A handy guide is about 30 ml of water per kilogram of body weight: at 70 kg that’s roughly 2.1 litres a day. The calculator works this out and converts it into glasses.

Importantly, all incoming fluid counts, not just plain water — tea, coffee, soups, vegetables and fruit provide water too. So you don’t always need to drink “N litres on top”.

What the norm depends on

Physical activity increases water loss through sweat — about half a litre is added per hour of intense exercise. Heat and dry air raise needs by a further 10–15%. Pregnancy and breastfeeding require more fluid.

The best guide is thirst and urine colour: pale yellow means you’re drinking enough, dark means a shortfall. Forcing yourself to drink beyond the norm isn’t beneficial.

When a doctor sets the amount

With kidney disease, heart failure and some hormonal disorders, fluid is restricted or increased — and only a doctor decides. In those cases follow your specialist’s advice, not a general calculator.

Frequently asked questions

Roughly about 30 ml per kilogram of weight: at 70 kg, about 2.1 litres. Needs rise in heat and with exercise. All fluids count — including tea, soups and juicy foods — not just plain water.
No, that’s a simplification. Needs are individual and depend on weight, activity and climate. The calculator gives a personal guide in litres and glasses for you.
Yes. Tea, coffee, soups, milk, and juicy vegetables and fruit provide water and count toward the daily total. The idea that coffee “dehydrates” is a myth — in moderation it also contributes to fluid balance.
A simple guide is urine colour: pale yellow means enough, dark means you should drink more. Go by thirst too; there’s no need to force water beyond the norm.
Yes, in rare cases excess water is dangerous (hyponatremia), especially with kidney or heart disease. That’s why in those conditions a doctor sets the amount, not a general calculator.

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This calculator is for reference and information only and gives a general guide. With kidney, heart or hormonal conditions, your doctor sets the fluid amount.