🔒 Calculated in your browser – nothing is sent

Water Intake Calculator

Estimate how much water you may need each day from your weight and exercise. Free and private.

How to use

Get a simple estimate of how much water you may need each day based on your weight and exercise. The calculator uses 35 ml per kilogram of body weight plus about 350 ml for every 30 minutes of exercise. Needs also depend on heat, health, pregnancy and diet, and food and other drinks contribute to your intake.

Enter your details.
Results update instantly.
Adjust the values to see how they change.

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Frequently asked questions

Is 8 glasses a day correct?

Eight glasses is a handy rule of thumb, not a requirement. Your needs depend on weight, activity, climate and health.

Does tea or food count?

Yes. Most drinks and the water in food count toward your total fluid intake.

Is it free?

Yes. Everything is free, with no sign-up and no limits.

Is my data stored or sent?

No. Calculations run in your browser and nothing you enter is sent or stored.

Can I rely on these results?

They use standard published formulas and give estimates for general information.

For general information only. This is not medical advice. Talk to your doctor, midwife or dietitian about your own situation.