Daily hydration target based on your body weight and activity level.Water Intake Calculator
How this is calculated
Your target is your body weight in kilograms multiplied by 0.033 litres, plus 0.35 litres for every 30 minutes of exercise you enter. Both figures are rules of thumb this site chose for being roughly right and easy to reason about — 0.033 L/kg puts a 70 kg adult at about 2.3 litres before exercise.
Limitations
This is a heuristic, not a published formula, and no study supports these specific numbers. Two things it deliberately ignores: official adequate-intake figures count the water in food as well as what you drink, so a drinking target derived this way is not comparable to them; and individual needs vary widely with climate, sweat rate, medication and pregnancy. Thirst and pale-yellow urine are better real-time guides than any arithmetic. If you have kidney or heart disease, or take diuretics, your fluid target is a clinical decision — ask your doctor rather than a calculator.
Frequently asked questions
How is daily water intake calculated?
The base formula is 33 ml per kg of body weight, with an additional 350 ml for every 30 minutes of daily exercise. This reflects current European Food Safety Authority and WHO guidance.
Does coffee or tea count toward water intake?
Mostly yes. At moderate doses (up to 400 mg caffeine/day), the mild diuretic effect of caffeine is offset by the water in the beverage. Plain water remains the best source, but coffee and tea do contribute.
Should I drink more in hot weather or high altitude?
Yes. Add at least 500 ml per hour of sweating activity in heat. At high altitude (above 2,500 m), increased respiration rate raises fluid loss — add 500–1,000 ml/day until acclimatised.
What are reliable signs of adequate hydration?
Pale yellow urine (straw-coloured) indicates good hydration. Dark yellow or amber signals dehydration. Clear urine may indicate over-hydration. Aim for pale yellow throughout the day.
Put it all together
The Health Planner reads your data and gives you exactly 3 actions for today.