How much water you should drink a day
Find out in seconds how many liters of water to drink per day. We estimate it from your body weight, activity level and climate, using the clinical reference of about 35 ml per kg, with adjustments for training and heat.
Rough estimate (drinking water; food adds more on top). Not medical advice.
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How is your water need calculated?
We start from a base of about 35 ml of water per kilo of body weight — the most widely used reference for healthy adults — and adjust it. Training adds roughly 500-750 ml per hour of exercise, because that is the order of magnitude most people sweat. Heat adds more. The result is a target for total fluid, not for glasses of plain water: coffee, tea, milk, soup and the water in fruit and vegetables all count towards it, and food alone typically supplies 20-30% of the total. Treat the number as a starting reference and let thirst and urine colour do the fine-tuning — they are better instruments than any formula.
How much water a day for your weight
The two-litres-for-everyone rule makes little sense: someone of 90 kg who trains needs nearly twice what a sedentary 50 kg person does. And note this is TOTAL water: between 20 and 30 % already comes from food, mostly fruit and vegetables.
| Weight | Normal day | With exercise or heat |
|---|---|---|
| 50 kg | 1.6 – 1.8 L | 2.1 – 2.4 L |
| 60 kg | 1.9 – 2.1 L | 2.5 – 2.8 L |
| 70 kg | 2.2 – 2.5 L | 2.9 – 3.3 L |
| 80 kg | 2.6 – 2.8 L | 3.3 – 3.7 L |
| 90 kg | 2.9 – 3.2 L | 3.7 – 4.2 L |
Estimated at 30 to 35 ml per kilo, consistent with EFSA adequate intakes for total water (2.0 L a day for women and 2.5 L for men, food included). Thirst and urine colour remain better guides than any number. These are reference ranges for healthy adults, not a diagnosis or individual advice.
FAQ
How many litres of water a day?
There is no universal figure. The "2 litres" rule is a rough average that ignores your weight, your training and the weather. This calculator scales it to you, which is why two people can land a litre apart and both be right.
Do coffee and tea count as water?
Yes. Despite the myth, the diuretic effect of caffeine at normal doses does not offset the fluid in the drink — the net contribution is positive. The same goes for tea, milk and soup. Alcohol is the genuine exception.
How do I know if I am drinking enough?
The simplest indicator is urine colour: pale yellow means well hydrated, dark yellow means drink more. Thirst is a reliable signal for most healthy adults, though it blunts with age, which is why older adults benefit from drinking on a schedule rather than on demand.
Can you drink too much water?
Yes, though it is rare. Drinking very large volumes in a short time can dilute blood sodium (hyponatraemia), which is dangerous. It shows up mostly in endurance events where people drink far beyond thirst. Spreading intake across the day avoids it entirely.