Daily Water Intake Calculator
Estimate your indicative hydration needs based on your weight, physical activity level and climate.
Parameters last reviewed on 05/09/2026 · Sources: EFSA — valores de referencia para el agua
Water is essential for almost every process in the body: it regulates body temperature, transports nutrients, aids digestion and removes metabolic waste. However, hydration needs are not the same for everyone — they vary depending on body weight, the intensity of physical activity and climatic conditions.
This calculator applies a common indicative formula: a base factor of 30 to 40 ml per kilogram of body weight, adjusted for your activity level, plus an extra amount in hot climates to compensate for fluid lost through sweating. The result is an indicative estimate of fluid intake. Bear in mind that part of your daily water (around 20-30%) also comes from food and other drinks, so not all of it needs to be drunk as water.
Recommended daily water intake
2.3 L
Equivalent to 9 glasses of water (250 ml each)
WHO minimum recommendation: 1.5 litres/day for adults.
Results are indicative only. Total water intake includes water from food and other drinks, not just water you drink. Hydration needs may vary for health reasons; consult a healthcare professional if you have any concerns. Indicative reference: EFSA (European Food Safety Authority), dietary reference values for water.
How your water needs are calculated
The starting point is your body weight, because fluid needs are proportional to the mass that has to stay hydrated. The formula multiplies your weight by a factor in millilitres per kilogram that rises with physical activity: 30 ml/kg if you are sedentary and up to 40 ml/kg if you train intensely almost every day. An extra 500 ml is added when you live or train in a hot climate, to compensate for the water you lose through sweat.
Worked example
A 70 kg person who is lightly active (factor 33 ml/kg) in a temperate climate would need 70 × 33 = 2,310 ml, or about 2.3 litres a day — the equivalent of just over 9 glasses of 250 ml. If that same person lived in a hot climate, they would add 500 ml and reach around 2.8 litres per day.
Millilitres per kilo by activity level
| Activity level | ml per kg | Example (70 kg) |
|---|---|---|
| Sedentary | 30 ml/kg | 2.1 L |
| Light | 33 ml/kg | 2.3 L |
| Moderate | 36 ml/kg | 2.5 L |
| Intense | 40 ml/kg | 2.8 L |
How to interpret the result
The figure you get is a daily guide, not a strict hour-by-hour obligation. The best approach is to spread it out by drinking steadily throughout the day rather than large amounts at once, and to use urine colour as a practical indicator: pale yellow means good hydration, while a dark shade tends to point to a low intake. On very hot days, during prolonged exercise, or with fever, diarrhoea or vomiting, your needs rise and it is wise to drink above the calculated figure.
Reliable signs you are drinking enough (and myths that are not)
The most practical indicator is not counting glasses but looking at urine colour: a pale yellow, similar to lemonade, indicates adequate hydration, while dark yellow suggests you should drink more. Frequency also helps: urinating every three or four hours during the day is typical. Thirst is a reliable mechanism in healthy adults, although it becomes less sensitive with age, which is why older people should drink on a schedule rather than waiting to feel it. Two myths are worth dismantling. First, that coffee and tea dehydrate you: their diuretic effect is mild and the net fluid balance remains positive, so they count towards the total. Second, that more water is always better: drinking far beyond your needs, especially in a short time, can dilute blood sodium and cause hyponatraemia, an uncommon but serious condition described in endurance runners.