Weight-based estimate
A common guideline is 35 ml of water per kg of body weight for sedentary adults — more if you are active.
Health calculators
Water Intake Calculator
Find your daily water target from weight and activity level.
Complete guide
How to use Water Intake Calculator
Enter your body weight (kg or lbs) and choose an activity level. The calculator estimates your daily water need at roughly 35 ml per kg and adds an activity multiplier, then shows the target in liters, fluid ounces, cups, and glasses.
Add about 500–750 ml for every hour of intense exercise, and drink more in hot climates.
Activity adjustment
Light to very-active levels apply a multiplier, since exercise and sweating raise your fluid needs.
Four easy units
See your target in liters, fluid ounces, cups, and number of 250 ml glasses so it's easy to track.
Answers
Water Intake Calculator FAQs
How much water should I drink per day?
A common guideline is 35 ml per kg of body weight for sedentary adults, with more for active people. The tool adjusts for your activity level.
Is the 8 glasses a day rule accurate?
It's a rough guide. A weight-based calculation tailored to your body and activity is more accurate.
Do coffee and tea count?
Caffeinated drinks are mildly diuretic but still contribute to hydration and are counted toward fluid intake by most health bodies.
Should I drink more when exercising?
Yes — add roughly 500–750 ml per hour of moderate exercise.
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