Water Intake Calculator
Daily water estimate based on body weight and activity.
How the estimate works
A common guideline is roughly 30–35 ml of water per kilogram of body weight per day, plus extra for exercise (about 350 ml per 30 minutes of activity). Food typically supplies ~20% of fluid intake, so the drinking target is lower than total needs.
Listen to your body
Thirst and pale-straw urine are good practical signals. Needs rise in heat, at altitude and during illness; some medical conditions require fluid limits — follow your doctor's advice first.
Frequently asked questions
Is 8 glasses a day right?
It is a rough average, not a rule. Body size and activity change the target a lot, which is what this calculator accounts for.