Water Intake Calculator
Daily hydration target adjusted for exercise and climate.
Deliberate exercise only. Adds about 600 ml per hour to replace sweat.
Daily water target
2.9 L
about 12 cups
What that looks like
- 500 ml bottles5.8
- 750 ml bottles3.9
- 1 L bottles2.9
- 8 oz glasses12.3
Spreading it through the day
- On waking0.35 L
- Mid-morning0.46 L
- With lunch0.46 L
- Afternoon0.58 L
- Evening0.46 L
Steady intake beats drinking large volumes at once — the kidneys can only process roughly 0.8-1 litre per hour.
How the Water Intake Calculator works
The '8 glasses a day' rule has no real evidence behind it. Actual needs scale with body weight, how much you sweat, and the climate you are in. This calculator starts from body weight and adjusts for exercise and heat.
Not medical advice. This calculator gives a general estimate, not medical advice. It cannot account for your individual health, medical history, or medication. Talk to a qualified healthcare professional before acting on any result.
Frequently asked questions
How much water should I drink per day?
A common starting point is 30-35 ml per kilogram of body weight, so about 2.1-2.5 litres for a 70 kg adult. Add roughly 500-700 ml per hour of exercise, and more in hot or humid conditions. The US National Academies suggest 3.7 L daily total fluid for men and 2.7 L for women, including water from food.
Does coffee or tea count toward my intake?
Yes. The diuretic effect of moderate caffeine is smaller than the fluid the drink provides, so coffee and tea are net hydrating. Food contributes another 20-30% of total intake, particularly fruit, vegetables, and soup.
How do I know if I am drinking enough?
Urine colour is the simplest indicator — pale straw means well hydrated, dark yellow means drink more, and completely clear may mean you are overdoing it. Thirst is a reliable signal for most healthy adults, though it dulls with age.
Can I drink too much water?
Yes, though it is rare. Consuming several litres in a short period can dilute blood sodium and cause hyponatremia, which is dangerous. Endurance athletes are most at risk. Spread intake through the day rather than drinking large volumes at once.