Water Intake Calculator
Daily recommendation based on body weight and activity – with an exercise surcharge
- Updated
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The DGE reference values depend on age.
Recommended drinking amount
liters per day
1.7L
1.7According to the DGE, at 80 kg you need about 35 ml per kg from drinks and food – 2.8 litres. You drink around 1.7 litres of that, food provides the rest.
Equivalent to approx.
Where the water comes from
- Drinks1.7 L62%
- Solid food1.1 L38%
- Water from drinks and food (35 ml/kg)
- 2.8 L
- Of which to drink
- 1.7 L
- Drinking amount per day
- 1.7 L
- DGE reference value for drinks in your age group (from 25 years)
- 1.4 L
Guidance, not a diagnosis. Based on the DGE reference values for water intake with normal energy intake; the surcharge for sport is an assumption. Heat, fever, pregnancy and breastfeeding increase the need; with heart or kidney disease, follow your doctor's advice.
How this was calculated
RZ-26 · headon.pro
Why drinking enough water matters
Fluid needs, effects of dehydration and practical tips
Water is the essential foundation for nearly all bodily functions: it regulates body temperature, transports nutrients and oxygen, removes metabolic waste products via the kidneys and skin, protects joints and organs, and is indispensable for digestion and cellular metabolism. The human body is 55–75% water. Even a fluid deficit of 1–2% of body weight can measurably impair concentration, mood and physical performance.
Our calculator uses the reference values of the German Nutrition Society (DGE): adults aged 19 to 50 need about 35 ml of water per kilogram of body weight – from drinks and solid food together. An 80 kg person thus needs 80 × 35 ml = 2.8 liters; according to the DGE ratio (1,410 ml from drinks to 860 ml from food) about 62 % of that is drunk, i.e. roughly 1.7 liters. From 51 to 64 years it is 30 ml/kg, children need more (up to 95 ml/kg). For sport the calculator adds a surcharge as an assumption.
Special population groups have different needs: pregnant and breastfeeding women need an additional 300–600 ml daily. Older adults often drink too little because the sensation of thirst decreases with age – deliberately scheduling drinking breaks is advisable here. Athletes doing long sessions should also take in electrolytes (sodium, potassium, magnesium) alongside water to avoid hyponatremia. People with kidney or heart conditions should discuss their individual fluid intake with their doctor, as too much fluid can be harmful.
Practical tips for drinking enough: start the day with a large glass of water. Always keep a bottle within reach. Use reminders on your smartphone or a drinking app. Flavor water with cucumber, lemon or mint if plain water is too bland for you. Unsweetened herbal teas and sparkling water also count fully towards your fluid intake. Pay attention to the color of your urine: pale yellow signals good hydration, darker urine indicates a fluid deficit.
Water intake overview
Factors that influence water needs
- Body weight
- DGE: 35 ml per kg (19–50 years) from drinks and food, of which about 62 % is drunk.
- Physical activity
- Depending on intensity, +0.5–1 L per training session. Sweat loss can be up to 2 L/hour.
- Temperature & climate
- Heat and high humidity significantly increase sweat loss. In summer, +0.5–1 L daily.
- Age
- Older adults have a weaker sense of thirst. Deliberate, scheduled drinking is important.
- Pregnancy
- Pregnant and breastfeeding women need an additional 300–600 ml daily for metabolism and milk production.
- Diet
- A diet rich in fruit and vegetables provides 500–700 ml of water daily through food.
Calculation examples
- Drinks and food (35 ml/kg)
- 80 × 35 = 2,800 ml
- Of which to drink (1,410 ÷ 2,270 ≈ 62 %)
- 1,740 ml
- Drinking amount per day
- 1.74 liters
- Drinks and food (35 ml/kg), of which to drink ≈ 62 %
- 2,450 ml → 1,520 ml
- Activity surcharge (assumption)
- +750 ml
- Drinking amount per day
- 2.27 liters
Frequently asked questions about the water intake calculator
Guideline values, sports, coffee and individual factors
How much water should I drink per day?
For adults aged 25 to 50, the German Nutrition Society (DGE) gives about 1.4 liters from drinks (1,410 ml) and about 860 ml from solid food. Per body weight this is 35 ml per kg for drinks and food together: at 70 kg that is 2.45 liters, of which about 1.5 liters are drunk. With physical activity, heat or certain medical conditions, needs can be considerably higher.
How much more water do I need when exercising?
During exercise, the body loses between 0.5 and over 2 liters per hour through sweating, depending on intensity, temperature and individual sweat rate. As a rule of thumb: light exercise (walking, yoga) adds 0.5 liters to the base requirement, moderate exercise (jogging, cycling) adds 0.75 liters, and intense training (strength/endurance sports) adds 1 liter or more. Drink before training already, and if in doubt, weigh yourself before and after exercise – each kilogram of weight lost corresponds to roughly 1 liter of fluid lost.
Can you drink too much water?
Yes, in extreme cases excessive drinking is dangerous. Hyponatremia (water intoxication) occurs when very large amounts of water are drunk in a short time, lowering the sodium level in the blood. For healthy adults, this is not a risk at normal fluid intake (under 4–5 liters daily without extreme endurance exercise). Endurance athletes at marathons or triathlons, however, should not drink excessive amounts of water without electrolytes.
Do coffee, tea and other drinks count towards fluid intake?
Yes, largely. Coffee and black tea have a net positive fluid contribution despite their mild diuretic effect, as the water they provide outweighs their diuretic effect. Alcohol, on the other hand, has a strongly dehydrating effect and does not count positively towards fluid balance. Sports drinks are useful during intense training with electrolyte losses. Water and unsweetened teas remain the best choice for daily fluid intake.
Does the weather affect my water needs?
Significantly. In heat and high humidity, fluid loss through sweating can increase considerably – even without physical activity. On hot summer days (above 30°C), you should drink 0.5–1 liter more than on cool days. In winter, heated, dry indoor air also increases water needs due to increased evaporation through breathing. Also note: older adults often consume too little fluid, as the sensation of thirst decreases with age.