Water Intake Calculator
A quick estimate of how much water to drink every day.
Not medical advice. This calculator gives a general estimate. It cannot diagnose or treat any condition. Please speak to a qualified doctor about your health.
A common rule of thumb is about 35 ml of fluid per kilogram of body weight, plus extra if you exercise or live in a hot climate. Part of your fluid comes from food, tea, milk and fruit.
Signs you need more
- Dark yellow urine
- Headache or tiredness
- Dry mouth and lips
People with kidney, heart or liver conditions sometimes need to limit fluids. If that is you, follow your doctor’s advice and not this estimate.
Last reviewed 7 November 2026. The formula and assumptions are shown above, and results are estimates, not advice.
Frequently asked questions
Does tea or coffee count?
Yes, mostly. They contribute to fluid intake, although water is the best default.
Can I drink too much water?
Yes, though it is rare. Drinking many litres in a short time can dilute blood sodium.