Water Intake Calculator
Estimate how much water to drink each day from your body weight and exercise, in litres, ounces and glasses.
For general information only — not medical advice. Results are estimates; talk to a doctor or qualified health professional about your own health.
How to use
- 1Enter your weight and how many minutes you exercise per day.
- 2Add extra if it's hot or you're pregnant or breastfeeding.
How it's calculated
Base = 35 ml per kg of body weight, plus about 350 ml for every 30 minutes of exercise. Food provides roughly 20% of total water intake.
Frequently asked questions
Do I really need 8 glasses a day?
Needs vary with size, activity and climate. EFSA suggests total water of about 2.5 L a day for men and 2.0 L for women, including water from food.
Do tea and coffee count?
Yes — moderate amounts of tea and coffee count toward hydration despite their mild diuretic effect.
How can I tell if I'm drinking enough?
Pale yellow urine and rarely feeling thirsty are good signs. Very dark urine suggests you need more.