About the Water Intake Calculator
About 60% of your body is water, and you lose well over 2 liters a day through sweat, urine and breathing. How much you need to replace depends mostly on your size and activity, which is why a common rule of thumb is about half your body weight (in pounds) in fluid ounces – roughly 30–35 ml per kilogram.
This calculator uses 33 ml/kg (0.5 fl oz/lb), adds about 12 fl oz for every 30 minutes of exercise and 17 fl oz on hot or sweaty days, and shows the result in ounces, glasses and bottles. Use the tracker below to tap in each glass or bottle you drink; it resets automatically at midnight.
How to use
- Choose lb/fl oz or kg/ml, then enter your body weight and how many minutes you exercise today.
- Tick the box if it is hot or you are sweating a lot.
- Read your daily target in fluid ounces, 8 oz glasses and 16.9 oz bottles.
- Each time you drink, tap + 1 glass or + 1 bottle to track your progress.
Daily water intake by body weight
| Body weight | Water per day | 8 oz glasses |
|---|---|---|
| 110 lb (50 kg) | 56 fl oz (1.6 L) | 7 |
| 130 lb (59 kg) | 66 fl oz (1.9 L) | 9 |
| 150 lb (68 kg) | 76 fl oz (2.2 L) | 10 |
| 180 lb (82 kg) | 91 fl oz (2.7 L) | 12 |
| 210 lb (95 kg) | 106 fl oz (3.1 L) | 14 |
Add roughly 12 fl oz for every 30 minutes of exercise and about 17 fl oz on hot days.
Easy ways to drink enough water
- Sip steadily through the day – a glass every hour or two works better than chugging a lot at once.
- Make it a habit: one glass when you wake up and one before each meal.
- Keep a refillable bottle on your desk or in your bag.
- Check your urine: pale yellow means you are well hydrated; dark yellow means drink more.
FAQ
Do I really need 8 glasses of water a day?
The “8×8” rule (eight 8-ounce glasses, about 2 liters) is an easy-to-remember guideline, not a scientific requirement. Smaller, less active people may need less; larger or very active people need more. The US National Academies put total water from all drinks and food at about 3.7 L a day for men and 2.7 L for women.
Can I drink too much water?
Yes. Drinking several liters in a short time can dilute the sodium in your blood (hyponatremia). Spreading your intake over the day avoids this.
Do coffee and tea count toward my water intake?
They do contain water, and moderate amounts of coffee or tea do count. Still, plain water, sparkling water or herbal tea are the best choices for most of your fluids; sugary drinks add a lot of calories.
Where is my water log stored?
Only in this browser on this device. Nothing is sent to a server, and the log starts again from zero each day.