Water Intake Calculator
Estimate how much water you should drink each day, adjusted for your body weight, activity level and climate.
A common guide is around 35 ml of fluid per kilogram of body weight, plus roughly 350 ml for every 30 minutes of exercise, with a further 10% for hot conditions and 20% for very hot conditions. Food typically supplies a further fifth of daily water, so treat this as a total fluid target rather than a fixed number of glasses. Anyone with heart or kidney conditions should follow medical advice on fluid intake.
Frequently asked questions
How much water should I drink a day?
A common guide is around 35 ml per kilogram of body weight, plus extra for exercise and hot weather. For a 70 kg adult that is roughly 2.5 litres a day from all drinks.
Does tea and coffee count towards water intake?
Yes. Despite the mild diuretic effect of caffeine, tea, coffee and other drinks still contribute to your daily fluid intake overall.
How much extra water do I need when exercising?
A practical rule is an extra 350 ml or so for every 30 minutes of moderate exercise, more in hot conditions. Thirst and urine colour remain useful everyday guides.
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