Water Intake Calculator
Enter your weight, how long you exercise and whether you live somewhere hot, and get a general daily water estimate in litres, ounces and glasses. It uses a simple rule of thumb and runs in your browser.
Runs in your browser. Your files are never uploaded.
Loading Water Intake Calculator…
How to use Water Intake Calculator
- Enter your weight and choose kg or lb.
- Enter how many minutes you exercise on a typical day.
- Choose a temperate or hot climate.
- Read the daily range in litres, ounces and 250 ml glasses.
The formula used
The base amount is 30 to 35 ml of water per kilogram of body weight. Then 350 ml is added for every 30 minutes of exercise, and 500 ml is added for a hot climate. The lower and upper figures give your range.
Reading the result
- A US fluid ounce is about 29.6 ml.
- A glass here means 250 ml.
- Spread your drinks through the day instead of drinking it all at once.
- Pale yellow urine usually suggests you are well hydrated.
When you might need more or less
Fever, vomiting, diarrhoea, high altitude and very dry air raise fluid needs. Some medical conditions and medicines mean you should drink less. This tool does not know about these, so use it as a rough starting point.
Limits
This is a general estimate and not medical advice. It does not cover pregnancy, breastfeeding, illness or medicines, and it is not for children. If you have a health condition, follow your doctor's advice. All calculation happens in your browser and nothing is uploaded.
Why use this water intake calculator tool
- Litres, ounces and glasses. The same estimate is shown in litres, millilitres, US fluid ounces and 250 ml glasses.
- Weight, exercise and heat. It starts from your body weight, then adds water for exercise and for hot weather.
- A range, not one number. You get a lower and an upper figure, because a single exact amount would be false precision.
- Private and free. Everything is calculated in your browser. Nothing is uploaded, and there is no account or sign-up.
Frequently asked questions
How much water should I drink a day?
There is no single answer. A common rule of thumb is 30 to 35 ml per kilogram of body weight, plus extra for exercise and heat. This calculator applies that rule and gives a range. It is a general estimate, not a medical target.
How much extra water do I need when I exercise?
The tool adds about 350 ml for every 30 minutes of exercise. Intense or long sessions, or heavy sweating, may need more. Drink to thirst and pay attention to the colour of your urine.
Does coffee, tea or food count?
Yes, in general. Drinks of all kinds and the water in food contribute to your total fluid intake. The result here is the total fluid you might aim for, not only plain water.
Can you drink too much water?
Yes, though it is uncommon. Drinking very large amounts quickly can lower blood sodium. Spread your drinks through the day and ask a doctor if you have kidney, heart or other conditions that affect fluids.
Is my weight sent to a server?
No. The calculation happens in your browser. Nothing is uploaded or saved.
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