Water Intake Calculator
Enter your weight to estimate how much water you should drink each day.
How this estimate is calculated
This calculator starts from a widely used baseline of about 33 ml of water per kilogram of body weight, then adds extra for exercise and hot climates, since both increase fluid loss through sweat.
Base = weight(kg) × 33ml
+ 350ml for every 30 minutes of exercise
+ 500ml if you're in a hot or humid climate
Frequently asked questions
Does this count coffee, tea, or other drinks?
This estimate is for total fluid intake, not just plain water. Coffee, tea, and other beverages contribute toward your daily total, though very high caffeine or alcohol intake can have a mild diuretic effect.
Is "8 glasses a day" still the right rule of thumb?
Not really — "8 glasses a day" (about 2 liters) traces back to a 1945 recommendation that actually included water from food, and has no strong scientific backing as a fixed number. Bodies vary too much in size, activity, and climate for one flat number to fit everyone, which is why authoritative guidance (like the U.S. National Academies) instead gives a range — roughly 2.7 liters/day for women and 3.7 liters/day for men from all fluids and food combined — and why this calculator scales its estimate to your own weight, exercise, and climate instead of using a single fixed target.
Should I drink more if I have a medical condition?
Some conditions (like kidney or heart issues) require fluid intake to be managed carefully, sometimes with a lower limit than general guidelines suggest. If you have a relevant medical condition, follow your doctor's specific guidance instead of a general calculator.