How much water should you drink per day?

A general guideline is about 30–35 ml per kilogram of body weight, meaning roughly 2–2.5 liters for a person weighing 70 kg. Exercise and hot weather increase the need. The calculator takes these into account.

Do coffee and tea count as fluid?

Yes, coffee, tea and the water contained in food all count. The mild diuretic effect of caffeine is minor. Plain water is still the best drink for quenching thirst.

How do I know if I'm drinking enough?

A good indicator is urine colour: pale means well hydrated, dark means drink more. Thirst, fatigue and headaches can also signal a fluid deficit.

Can you drink too much water?

Drinking very large amounts (several liters in a short time) can cause a dangerous imbalance in salt levels. Normal thirst-guided drinking is safe.

Water Intake Calculator — Daily Needs

Name: Water Intake Calculator — Daily Needs
Author: Miikka

Calculate how much water you should drink per day by weight, exercise and weather. Stay hydrated. Free water calculator.

By Miikka · CalcBrew · Updated Sep 16, 2026

Weight: 154 lb

Exercise per day: 30 min

Weather: Normal

89.9 fl oz

Daily water need

Base need	78.1 fl oz
Extra for exercise	11.8 fl oz
Daily water need	89.9 fl oz
In glasses (200 ml)	13 glasses

ℹ️ The estimate is based on about 33 ml of water per kg of body weight, adjusted for exercise and weather. Part of your fluid comes from food. Listen to your body — thirst and pale urine are good indicators.

This water intake calculator estimates how much you should drink each day based on your weight, exercise and the weather. You get a clear figure in litres plus a glass count, making it easy to track your hydration.

How the calculator works and what it’s for▾

How daily water needs are calculated

The calculator starts from a baseline of about 33 millilitres of water per kilogram of body weight. To that it adds extra need from exercise and the effect of the weather, since heat and sweating increase fluid loss.

For example, a person weighing 70 kilograms has a baseline of just over two litres, and on an active day the total need rises clearly above that.

What you enter and what you get

Enter your weight, your daily exercise in minutes, and select the current weather.

You get your baseline need, the extra need from exercise and your total daily requirement in litres, plus the same amount expressed as two-decilitre glasses to make the goal concrete.

Who it is for and when

The tool suits anyone who wants to make sure they stay hydrated in everyday life, during sport or on hot summer days.

It is also useful when you feel tired or have a headache for no obvious reason, since mild dehydration is a surprisingly common cause.

Good to know

Part of your daily fluid comes from food, so you do not need to drink all of it as water. Listen to your body: thirst and pale urine are good signs of adequate hydration.

The figures are rough estimates. If you have a condition or medication that affects fluid balance, follow your doctor's advice first.

🔄 Reviewed June 2026

Frequently asked questions

Cite this calculator

APACalcBrew. (2026). Water Intake Calculator — Daily Needs. https://calcbrew.com/water-intake-calculator

MLA“Water Intake Calculator — Daily Needs.” CalcBrew, 2026, calcbrew.com/water-intake-calculator.

Link to https://calcbrew.com/water-intake-calculator. Results are estimates; cite the underlying formula or data source for academic work.

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