Is the 8 glasses per day rule accurate?

The 8×8 rule (eight 8-ounce glasses) is a rough approximation. Actual needs vary by body weight, activity level, climate, and health status. Most adults need 2-3.5 liters per day from all sources including food.

Do coffee and tea count toward hydration?

Yes - caffeinated beverages do contribute to overall fluid intake despite mild diuretic effects. However, each cup of coffee offsets hydration slightly, so adding a glass of water per cup is a common recommendation.

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Water Intake Calculator

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Weight (kg)

Activity level

Climate

Age group

Wake time (hour, 0–23)

Sleep time (hour, 0–23)

Coffees / teas today (+1 glass each)

Alcoholic drinks today (+1 glass each)

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Calculate daily water needs based on weight (0.033 L/kg), activity level, and climate. Results in liters, ml, cups, fl oz, and glasses. Hourly hydration schedule included.

How to Use

1Enter your body weight and select the unit (kg or lbs)
2Choose your activity level (sedentary, moderate, or active)
3Select your climate (cool, moderate, or hot)
4Click Calculate to see daily water intake in liters, cups, fl oz, and glasses
5The hourly hydration schedule distributes your intake across your waking hours

Features

Weight-based formula (0.033 L/kg) adjusted for activity and climate
Results in liters, ml, cups, fl oz, and 8-oz glasses
Hourly hydration schedule over waking hours
Coffee/alcohol offset note
Dehydration warning signs panel
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Water Intake Calculator

How to Use

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