Daily Water Intake Calculator

A rough daily fluid guide based on body weight and activity.

Suggested daily fluid

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In cups (240 ml)

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In fluid ounces

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From body weight

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Added for activity

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A rough general guide, not medical advice. Needs vary with climate, health and pregnancy, and fluid from food counts too. Let thirst and how you feel guide you, and follow your clinician’s advice for any medical condition.

Where the estimate comes from

A common rule of thumb is around 35 ml of fluid per kilogram of body weight per day, with a little extra to replace what you sweat out during exercise. That gives a ballpark total — including the fluid you get from food and other drinks, not just plain water.

fluid ≈ 35 ml × weight (kg) + activity allowance

Treat it as a loose target rather than a quota. Real needs swing with the weather, how hard you move, what you eat, and your health, so the best everyday guides remain your thirst and the colour of your urine.

Worked example

Around 35 ml per kilogram suggests roughly 2.45 litres a day for a 70 kg adult, plus about 350 ml for 30 minutes of exercise — close to 2.8 litres, or about 12 cups, including fluid from food and other drinks.

Staying comfortably hydrated

Most healthy people regulate fluid well without counting millilitres. Spreading drinks across the day, topping up around exercise and in the heat, and listening to thirst covers the basics. Fixating on a precise number is rarely necessary.

Gentle pointers

Food counts. Fruit, vegetables and soups contribute a meaningful share.
Context matters. Heat, altitude, illness and activity all raise needs.
Check with a professional. Some conditions require specific fluid guidance.

This is general information, not medical advice.

Frequently asked questions

Is there a single right amount?

No. Needs vary with climate, activity, body size, diet, health and pregnancy. This is a rough guide; your thirst and the colour of your urine are practical day-to-day signals.

Does food count toward fluid?

Yes. Fruit, vegetables, soups and most drinks all contribute, often a fair share of the total. The figure here is total fluid, not water from the tap alone.

Can I drink too much?

In rare cases, very large amounts in a short time can be harmful. For almost everyone, spreading normal fluid through the day is fine — but if you have a medical condition, follow your clinician’s advice.

How does exercise change it?

Sweating raises your needs, so the estimate adds a little for activity. Hot weather and intense or long sessions increase it further — drink to thirst and replace what you lose.