Water intake calculator
Estimate how much water to drink a day from your weight, your exercise and the weather.
Drink about
A general estimate for healthy adults, not medical advice.
How it works
water (ml) = 33 × weight (kg) + 12 × exercise minutes (+ 500 in heat)33 ml per kilogram is a common baseline; exercise adds about 350 ml per 30 minutes.
Worked example
70 kg, 30 minutes of exercise, mild weather:
- 33 × 70 = 2,310 ml
- 12 × 30 = 360 ml
- About 2.7 L, roughly 11 glasses of 250 ml
Frequently asked questions
Does food count toward water intake?
Yes. About 20% of the water we take in comes from food. The amount here is what to drink, food aside.
Is the 8 glasses a day rule right?
It is a rough rule. Needs grow with body weight, exercise and heat; the European Food Safety Authority suggests about 2.0 L of total water a day for women and 2.5 L for men.
Can I drink too much?
Yes, very large amounts in a short time are dangerous. People with heart or kidney conditions should follow their doctor’s advice on fluids.