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Open Calculator โOverview
The 8-glasses rule ignores body weight and activity level. Your actual water needs vary significantly from person to person.
The Formula
Daily Water (ml) = Weight (kg) ร 35 ร Activity Multiplier
Standard formula used by professionals worldwide
Worked Example
Step-by-step
60kg sedentary person โ 2,100ml | 80kg athlete โ 80ร35ร1.6 = 4,480ml
Key Concepts
- Accuracy: Results are as accurate as the inputs you provide
- Units: Always use consistent units throughout your calculation
- Verification: Double-check important calculations before making decisions
- Professional advice: For major financial, health, or structural decisions, consult a qualified professional
Privacy and Security
- All calculations run entirely in your browser
- No data is sent to any server
- No sign-up or personal information required
- Your data stays private โ always
Frequently Asked Questions
Does food count toward intake?
Yes โ about 20% of daily water comes from food, especially fruits and vegetables.
Signs of dehydration?
Dark yellow urine, headache, fatigue, dry mouth, reduced concentration.
Can you drink too much?
Yes โ hyponatremia from excessive water is rare but dangerous in endurance sports.