💧 Water Intake Calculator
Water needs scale with body size and activity: a 90 kg athlete in summer needs far more than a 55 kg office worker. The common eight-glasses rule ignores both factors completely.
This calculator estimates your daily water target from your weight plus an activity adjustment, and shows it in liters, glasses and fluid ounces so you can track it however you like.
How to use this calculator
Enter your weight in kilograms, pick the activity level closest to your day, and read your personalized daily target.
- Type your body weight in kg.
- Choose your activity level.
- Read your daily target in liters, glasses and ounces.
How Much Water Should I Drink Daily?
A solid baseline is about 33 ml per kilogram of body weight — so a 70 kg person needs roughly 2.3 liters before activity. Add around 350 ml for moderate exercise, 700 ml for intense training, and up to a liter extra in hot weather or heavy sweating. About 20 percent of daily water comes from food, especially fruit and vegetables, so your drinking target is slightly lower than total water needs. Pale-yellow urine is the simplest real-world check that you are drinking enough.
Frequently asked questions
How much water should I drink per day?
Roughly 33 ml per kilogram of body weight plus extra for activity — about 2.3-3 liters for most adults. Use the calculator above for your personal number.
Is 8 glasses of water a day enough?
For many people it is close, but it ignores body size and activity. A large active person may need 12+ glasses while a small sedentary person needs fewer.
Can you drink too much water?
Yes — overhydration can dilute blood sodium (hyponatremia), which is dangerous. Do not force gallons; drink to thirst plus your calculated baseline.
Does coffee count toward water intake?
Mostly yes. Caffeine is mildly diuretic but coffee and tea still contribute net hydration. Water remains the best choice, though.
How do I know if I am dehydrated?
Dark yellow urine, headache, fatigue and dizziness are classic signs. Pale straw-colored urine generally means you are well hydrated.