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Piz Sardona Akademie

Interactive tool

Water intake calculator

How much water a day is enough? The calculator turns body weight, age, exercise and temperature into a personal guide value for your daily intake.

70 kg
Your daily guide value2.1–2.5 lroughly 9 glasses of 2.5 dl
or roughly 3 glass bottles of 75 cl
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How the amount spreads across the day
Morning
0.7 l
Midday
0.6 l
Afternoon
0.6 l
Evening
0.5 l

A guide value for healthy adults, not medical advice. If you have a heart or kidney condition, are pregnant or breastfeeding, or are unsure, please discuss your fluid intake with a doctor.

How this guide value is calculated

A common rule of thumb for healthy adults is 30 to 35 millilitres of fluid per kilogram of body weight per day. European expert bodies cite a total intake of around 2 litres for women and 2.5 litres for men as a reference — this includes the water contained in food, which contributes roughly a fifth to a quarter depending on your diet.

Exercise and heat increase your needs: when you sweat, you lose fluid and minerals. The calculator therefore adds around 4 decilitres per half hour of exercise, and half a litre on hot days. Beyond that, trust the body's simplest signal — thirst.

Age and stage of life factor in as well: from 51 the calculator uses a slightly lower band of 28 to 33 millilitres per kilogram, because the joint German-Austrian-Swiss (D-A-CH) reference values for water intake — which include the water contained in food — drop from around 35 to around 30 millilitres at this age. Needs rise during pregnancy and breastfeeding — here the calculator adds the EFSA reference values of 0.3 and 0.7 litres per day respectively.

Five simple habits for drinking more water

  • Keep water within reach: a carafe on your desk or a bottle on the go is its own reminder to drink.
  • Plan fixed moments: short reminders — a note or your phone — help you not to forget drinking.
  • Eat water-rich foods: cucumber, melon, tomatoes or oranges contribute additional fluid.
  • Vary the taste: lemon, lime, cucumber or mint bring variety to the glass.
  • Anchor routines: a glass of water after getting up and with every meal turns drinking into a habit.

Frequently asked questions

Do coffee and tea count towards my intake?

Yes. Coffee and tea contribute to your fluid intake — the old idea that coffee “dehydrates” the body is considered outdated at normal consumption levels. Water remains the best base, though, because it is calorie-free.

Does the guide value apply to children, pregnant women or older people?

The calculator is designed for adults: age, pregnancy and breastfeeding can be set directly and feed in via reference values. It does not apply to children — their needs differ considerably. If you have a medical condition, a conversation at your doctor's practice remains the reliable guide.

Do I have to hit the amount exactly?

No. The value is a rough guide for the day, not a target. Thirst remains a clear signal — as does urine colour: pale yellow indicates you are drinking enough.

Does it matter whether I drink still or sparkling water?

Not for hydration — both count fully towards your intake. Carbonation is a matter of taste and tolerance: if it bothers you, choose still or lightly sparkling water.

How much should I drink during sport?

As a guide, add around 4 decilitres per half hour of intense exercise, spread across before, during and after. Heavy sweating costs you minerals such as sodium and magnesium as well as fluid — after long, intense sessions, pay attention to replacing them through food and drink.

How do I notice that I have been drinking too little?

Early signs are thirst, darker urine, headaches and flagging concentration. If you know these signals, you can counter them early — most easily with fixed drinking habits across the day.

Why does the sex setting not change the guide value?

Because the calculator works from body weight, which already captures most of the difference. The setting instead shows the matching EFSA reference value: around 2.0 litres of total intake per day for women, 2.5 litres for men.