Water Intake Calculator
Calculates daily water needs based on body weight (35ml/kg baseline) plus exercise adjustment (500ml per active hour). H...
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How It Works
Calculates daily water needs based on body weight (35ml/kg baseline) plus exercise adjustment (500ml per active hour). Hydration needs increase with heat, altitude, illness, and pregnancy.
Quick Reference
70kg, sedentary
70×35ml
2.45L/day
80kg, 1hr exercise
80×35+500ml
3.3L/day
8 glasses rule
8×240ml
1.92L (rough guide)
Tips & Shortcuts
Urine color is the best real-time hydration indicator: pale yellow = good, dark yellow = drink more.
Thirst is a late signal of dehydration — drink proactively throughout the day.
Coffee and tea count toward fluid intake, despite mild diuretic effect.
Common Mistakes
Drinking the same amount regardless of activity or climate
Needs increase by 500-1000ml/hour during intense exercise and in hot environments.
Drinking all water at once instead of throughout the day
Kidneys can process ~800-1000ml/hour. Spreading intake is more effective.
Frequently Asked Questions
The general baseline is about 0.5 oz per pound of bodyweight (30ml/kg). For a 160 lb person, that is 80 oz (2.4 liters) before accounting for exercise or heat.
Yes. You lose 500–1,000ml of fluid per hour of moderate exercise. Add approximately 400–600ml (12–20 oz) for every 30 minutes of intense exercise.
Yes. Coffee and tea contribute to daily fluid intake. The water content outweighs the mild diuretic effect for moderate consumption.
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