Water Intake Calculator
Get a daily hydration target that fits you. Based on your body weight, exercise and climate, shown in ounces, liters and 8-ounce glasses.
Drink about
General estimate for information only, not medical advice. People with kidney, heart or other conditions should follow their doctor's fluid advice.
How to use the water intake calculator
- Enter your body weight and choose units.
- Add your typical daily exercise and choose your climate.
- Use the result as a daily target, spread through the day.
How much water do you really need?
A common rule of thumb is about half an ounce of water per pound of body weight (roughly 33 ml per kg), plus about 12 ounces (350 ml) for every 30 minutes of exercise. Hot weather, high altitude, pregnancy and breastfeeding all increase needs. This calculator combines those adjustments into a single daily target.
The US National Academies set adequate total water intake at about 3.7 liters a day for men and 2.7 liters for women, but that includes water from food, which typically supplies about 20%. Coffee, tea, milk and other drinks count toward your total too.
Your body is good at signaling thirst, and pale yellow urine is a simple sign you are well hydrated. It is possible to drink too much water, especially during long endurance events, so there is no benefit to forcing far more than your body needs.
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Frequently asked questions
Do I need 8 glasses a day?
The "8×8" rule (64 oz) is a reasonable baseline for many adults, but needs vary with size, activity and climate.
Does coffee count?
Yes. Caffeinated drinks have a mild diuretic effect but still contribute to your daily fluid intake.
Can you drink too much water?
Yes. Drinking large amounts very quickly, especially during long endurance exercise, can dangerously lower blood sodium.
Is this medical advice?
No. Follow your doctor's guidance if you have a medical condition that affects fluid balance.