Daily Water Intake Calculator
Estimate how much water you should drink each day based on your body weight and activity. The result comes in liters, cups and standard glasses — because "8 glasses a day" was never one-size-fits-all.
How to use this calculator
- Enter your weight in kg.
- Enter your typical exercise minutes per day — sweat losses need replacing.
- Select a hot climate if you live somewhere hot or humid.
- Press Calculate for your daily target in liters, cups, glasses and bottles.
Formula used
The 30–40 ml-per-kg guideline is a widely used clinical rule of thumb; this calculator uses 35 ml/kg. Exercise addition reflects typical sweat losses. Total fluid needs include water from food and other beverages.
Example calculation
A 70 kg person exercising 30 minutes/day in a temperate climate:
70 × 35 = 2,450 ml + 350 ml exercise = 2.8 liters/day — about 11 cups or 5½ standard bottles. In a hot climate, the target rises to ~3.3 liters.
How much water do you actually need?
Fluid needs scale with body size, activity and environment, which is why fixed rules like "8 glasses" miss for many people. Health authorities put typical total fluid intake around 2.7 L/day for women and 3.7 L/day for men — but roughly 20% of that arrives through food, and coffee, tea and milk all count toward hydration too.
Your body regulates this remarkably well: thirst plus urine color (aim for pale yellow) track hydration status better than any formula. The calculated target is most useful as a daily anchor — especially for people who genuinely forget to drink at a desk all day.
Why use this calculator?
- Get a personal target based on your weight and training instead of a generic 8-glass rule.
- See the target in bottles and cups — units you can actually track through the day.
- Adjust properly for exercise and hot weather, when needs rise the most.
Frequently asked questions
How much water should I drink a day to lose weight?
Water doesn't burn fat, but drinking ~500 ml before meals has been shown to modestly reduce calorie intake, and replacing sugary drinks with water cuts real calories. Your target from the calculator is a good baseline either way.
Do coffee and tea count toward my water intake?
Yes. Despite the caffeine-dehydration myth, moderate coffee and tea contribute net positive hydration. Alcohol is the exception — it genuinely dehydrates.
Can I drink too much water?
Yes, though it's rare. Drinking many liters in a short period can dilute blood sodium (hyponatremia), which is dangerous. Spread intake through the day and let thirst guide you during long endurance events, alongside electrolytes.
What are the signs of dehydration?
Dark yellow urine, thirst, headache, fatigue and reduced concentration are early signs. Urine the color of pale straw generally means you're well hydrated.