Water Intake Calculator
Estimate how much water to drink a day from your weight, exercise and climate. Results in litres, glasses, cups and fluid ounces. Free.
- Glasses (250 ml)
- 12
- US fluid ounces
- 101
- US cups
- 12.6
An estimate from a published formula, for general information. It isn't medical advice; talk to a doctor or dietitian about your own needs.
A starting point for hydration
A common guide is about 35 ml of water per kilogram of body weight a day, plus extra for exercise (roughly 0.35 litres for every 30 minutes) and hot weather. The European Food Safety Authority suggests total water intake of about 2.0 litres a day for women and 2.5 litres for men, which includes water from food (usually 20–30%) as well as drinks. Tea, coffee, milk and water-rich foods all count. Thirst and pale yellow urine are good everyday signs that you're drinking enough.
How to use it
- 1
Enter your weight
In kilograms or pounds.
- 2
Add your exercise
Minutes of exercise on a typical day, and tick hot weather if it applies.
- 3
Read your target
In litres, glasses, cups or fluid ounces.
Frequently asked questions
Do I really need 8 glasses a day?
The '8 × 8' rule (8 glasses of 8 oz, about 2 litres) is a rough guide, not a scientific rule. Needs depend on your size, activity and climate.
Does coffee count towards water intake?
Yes. Coffee and tea are mildly diuretic, but they still add to your total. So do milk, soups, fruit and vegetables.
Can you drink too much water?
Yes, though it's rare. Drinking several litres in a short time, for example during endurance events, can dangerously lower blood sodium.
Is anything sent to a server?
No. Everything is calculated in your browser, and nothing you type is stored or sent anywhere.