Water Intake Calculator
A daily water target from body weight, exercise, climate and pregnancy or breastfeeding
100% free. Runs entirely in your browser - your files and data never leave your device and nothing is uploaded to any server.
Units
Climate
Extra
Food also supplies water. Thirst, urine colour and medical conditions (kidney, heart, hyponatremia risk) matter more than any formula.
Estimates only. Not medical advice and not a diagnosis. Talk to a clinician about your own numbers. Base is 35 ml per kg, plus 350 ml per 30 minutes of exercise.
About this tool
A common planning figure is 35 ml of water per kilogram of body weight, plus extra for exercise, heat, pregnancy or breastfeeding. Food also contains water. Pale-yellow urine and thirst are better day-to-day guides than any litre target, and some heart or kidney conditions need a fluid limit. Forcing gallons of water can cause hyponatremia. Estimates only. Not medical advice.
How to use this tool
- Enter body weightKilograms or pounds. The formula converts internally.
- Add exercise minutes and climateThis model adds 350 ml per 30 minutes of exercise and 500 ml on hot or humid days.
- Read litres, US fl oz and 250 ml glassesSpread drinks through the day rather than chugging a huge volume at once.
Key features
- Scales with weight instead of a fixed eight glasses.
- Exercise, climate and pregnancy or breastfeeding extras.
- Litres, millilitres, US fl oz and 250 ml glasses.
- A cap so the page will not suggest more than 6 litres.
Common uses
- A first daily target when someone asks "how much water should I drink".
- Extra water on a hot training day.
- A pregnancy extra of 300 ml in this model, which is a sketch, not a prescription.
Tips for better results
- Urine that is pale straw is a better check than hitting a litre number.
- Caffeine and alcohol still count as fluid but they are not a reason to skip water.
- If a clinician has limited your fluids, ignore this page.
Mistakes to avoid
- Chugging 3 litres in an hour before a weigh-in or a race.
- Ignoring thirst because an app said 4 litres.
- Using this as treatment for oedema, heart failure or kidney disease.
Frequently asked questions
It can land close for a smaller adult. This page scales with weight and activity instead of a fixed eight.
Yes. Hyponatremia is real in endurance events and in people who force gallons of water. Do not chase a number past thirst if a clinician has limited your fluids.
Yes, water in food and other drinks contributes. The litre target here is a total-fluid sketch, not "plain water only".
Yes. It is free for normal use with no account required.
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