🌿 free · private · no signup
Water Intake Calculator
Work out how much water to drink a day from your sex, exercise and the weather, in litres, fluid ounces and glasses, with an animated bottle and simple tips to drink more. Based on the National Academies' adequate intake.
How much water should I drink?
A general guide for healthy adults. Food gives you about a fifth of your water; this is the drinking part.
Aim to drink about
2.5 L
a day, about 10 glasses of 250 ml (8.5 oz).
Base 2.2 L + exercise 0.3 L
How we work it out
- The US National Academies set an adequate intake of total water of about 2.7 L a day for women and 3.7 L for men, from drinks and food together. About 80% comes from drinks: roughly 2.2 L and 3.0 L.
- Exercise: we add about 0.3 L for every 30 minutes. Hot or humid weather: we add 0.5 L.
- A simple check: pale yellow urine usually means you're drinking enough. Water, milk, tea and coffee all count.
✅ Rules last checked:
📚 Official sources: National Academies: Dietary Reference Intakes for water
We build every tool from the official rules and re-check them when they change. Always confirm with the official source before you rely on a result.
🛠️ Spotted a mistake or an out-of-date rule? Tell us
Guides
Related tools
Questions people ask
Is 8 glasses a day right?+
It's a good rough guide. The National Academies suggest about 2.7 litres of total water a day for women and 3.7 litres for men, from all drinks and food. Food gives about a fifth, so drinks are roughly 2.2 litres (9 glasses) for women and 3 litres (12 glasses) for men.
Do tea and coffee count?+
Yes. All drinks count towards your water, including tea and coffee. Water is the best everyday choice because it has no sugar or calories.
How do I know I'm drinking enough?+
Pale yellow urine and rarely feeling thirsty are good signs. Drink more when it's hot or when you exercise.
Can you drink too much water?+
Yes, though it's rare. Drinking very large amounts in a short time can be dangerous. If you've been told to limit fluids for a health reason, follow your doctor's advice.