Water Intake Calculator
Calculate daily hydration needs
Formula
Base: 30-35 mL per kg
Active: Add 500-1000 mL
Hot climate: Add 500 mL
Quick Reference
| Sedentary | 30 mL/kg |
| Active | 35-40 mL/kg |
| Athlete | 40-50 mL/kg |
| Hot Weather | +500 mL |
Related
Complete Guide to Water Intake Calculator
Proper hydration is essential for every bodily function - from regulating temperature and transporting nutrients to supporting brain function and physical performance. Even mild dehydration (1-2% body weight loss) can impair cognitive and physical performance.
How Much Water Do You Need?
The classic "8 glasses a day" is a rough guide, but actual needs vary based on body size, activity, climate, and diet. A better formula is 30-35 mL per kg of body weight, adjusted for activity and environment.
Signs of Proper Hydration
- Urine is light yellow (not clear, not dark)
- You urinate every 2-4 hours
- No persistent thirst or dry mouth
- Good energy levels and mental clarity
Water from Food
About 20% of daily water comes from food, especially fruits and vegetables. Cucumbers, watermelon, and lettuce are 95%+ water. Coffee and tea count toward hydration despite mild diuretic effects.
Exercise Hydration
Drink 500 mL 2 hours before exercise, sip during activity, and replace lost fluids after. For intense exercise over 60 minutes, consider drinks with electrolytes. Weigh yourself before and after - drink 500 mL for every 0.5 kg lost.
Frequently Asked Questions
A good baseline is 30-35 mL per kg of body weight. For a 70kg person, that's about 2.1-2.5 liters. Adjust up for exercise, hot weather, or high altitude. Listen to your thirst and check urine color.
Yes! Despite mild diuretic effects, coffee and tea still contribute to hydration. Regular coffee drinkers develop tolerance to the diuretic effect. Don't count alcohol - it's a significant diuretic.
Yes, though rare. Hyponatremia (low sodium from excess water) can occur in endurance athletes or those forcing excessive intake. Drink to thirst, don't force liters beyond what feels natural.
Light yellow like lemonade indicates good hydration. Clear means you're potentially overhydrating. Dark yellow or amber suggests dehydration. First morning urine is normally darker.
It's a reasonable starting point for average adults but doesn't account for body size, activity, or climate. The mL/kg method is more personalized. 8 glasses (2L) is close to right for a sedentary 60kg person.
Drink 500 mL 2-3 hours before exercise. Sip 150-250 mL every 15-20 minutes during exercise. After, drink 500 mL for every 0.5 kg of body weight lost during the workout.
Yes, sparkling water hydrates equally well. Some people find it causes bloating, but there's no hydration difference. Avoid varieties with added sugar or sodium if those are concerns for you.