Water intake calculator
A daily drinking target from your bodyweight, with extra for training and hot weather. It counts what you drink, not the water already in your food.
Water Intake Calculator
A common daily water target is about 35 ml per kg of bodyweight, plus roughly 600 ml for every hour of exercise and another 500 ml in hot weather. An 80 kg adult who trains for an hour therefore needs about 3.4 litres a day. Food supplies around a fifth of total water on top, and pale-straw urine is the simplest check that intake is enough.
About 14 glasses of 250 ml
Method notes (2)
- 35 ml per kg of bodyweight, plus about 600 ml per hour of exercise and 500 ml on a hot day. Food adds roughly a fifth on top.
- Pale-straw urine is the simplest check that the target suits you. Heavy sweaters and long sessions need more, and electrolytes as well as water.
Metric or imperial · runs the same code as the app · nothing is sent anywhere
How it works
water = 35 ml × kg + 600 ml × hours of exercise + 500 ml if hot, rounded to the nearest 50 ml. The 35 ml/kg base is the usual clinical rule of thumb; the exercise allowance covers typical sweat losses of 0.5 to 1 litre an hour.
The European Food Safety Authority sets adequate total water at 2.5 litres a day for men and 2.0 for women, food included. About a fifth of that usually comes from food, so the drinking target here sits a little under the total for most people and above it for heavier or more active ones.
Common questions
Do coffee and tea count toward water intake?
Yes. The mild diuretic effect of caffeine is outweighed by the fluid in the drink for regular drinkers, so coffee and tea count. Alcohol is the exception worth not counting.
Can you drink too much water?
Yes, though it takes a lot. Drinking several litres in a few hours, especially during long endurance events without salt, can dilute blood sodium dangerously. Spread intake through the day and add electrolytes on long, sweaty sessions.
Is 8 glasses a day right?
It is a reasonable floor for a small, inactive adult, about 2 litres. Larger and more active people need more, which is why this works from bodyweight and exercise instead.
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