Water Intake Calculator
How much water should you drink a day? Weight-based hydration target.
The Water Intake Calculator estimates your daily hydration target from body weight plus exercise: roughly 33 ml per kilogram of body weight, with extra fluid added for activity. Results appear in liters, cups and fluid ounces so the target works no matter how you measure.
Hydration needs are personal — hot climates, heavy sweating and training days all raise them — so the guideline comes with practical signals: pale-yellow urine and regular thirst mean you are roughly on track, while dark urine and headaches are the body asking for more.
The estimate runs entirely in your browser and is deliberately simple: body weight is the strongest single predictor of baseline needs, and the activity add-on covers the most common variable. Use it as a daily anchor, then adapt to how you feel.
Daily water target
2.8 liters
≈ 96 fl oz
In cups
11.8 cups
≈ 240 ml cups
Per hour (awake)
0.18 L/h
≈ 16 waking hours
Guideline: ~33 ml per kg of body weight plus ~0.35 L per 30 minutes of exercise. Needs rise with heat, humidity and sweat rate — urine color and thirst remain the practical signals.
How to use the Water Intake Calculator
- Enter your body weight (kilograms or pounds).
- Optionally add your daily exercise in minutes.
- Read your target in liters, cups and fluid ounces.
- Spread intake across the day rather than gulping it.
- Use urine color as the practical daily check.
Frequently asked questions
Is the '8 glasses a day' rule accurate?
It is a memorable approximation, not science. Weight-based guidance (≈33 ml per kg) is closer to reality: a 75 kg person needs about 2.5 liters — roughly 10 glasses — and more with exercise or heat.
Does coffee and tea count toward water intake?
Yes — caffeinated drinks are mildly diuretic but still mostly hydrating, and modern guidance counts them toward total fluid. Food also contributes roughly 20% of daily water for most people.
Can I drink too much water?
Rarely, but endurance athletes and extreme intakes can cause hyponatremia (low blood sodium). If you are drinking far beyond thirst for hours of sweating, include electrolytes. Kidney and heart conditions warrant medical guidance on fluid limits.
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