Hydration Calculator
Measure your daily fluid goal the way sports scientists do — by body weight, sweat loss and environment, not by counting glasses.
Fill in your details to see your daily goal
Hydration Is a Balance, Not a Number of Glasses
Your body loses roughly 2.5 liters of fluid a day through breath, skin and urine — more when you train or live in the heat. Because every liter lost has to be replaced, hydration advice that ignores body size and sweat rate is essentially noise. That's why this hydration calculator starts from your weight: a bigger body has more tissue to keep hydrated, so the baseline scales at about 35 ml per kilogram. Exercise and hot climates each add clear, evidence-based amounts on top, following EFSA and IOM reference values for total daily fluid intake.
Treat the result as your daily anchor point. Coffee, tea, milk and juicy food all count toward it; alcohol works against it. Recheck your number whenever your training load, weight or season changes — a summer result can be half a liter higher than your winter one.
Turning the Number Into a Habit
People who hit their hydration goal reliably rarely rely on willpower alone. They anchor drinking to fixed moments: a glass on waking, one before each meal, a bottle on the desk refilled twice a day. If your target is 2.8 liters, that's one 500 ml bottle with breakfast, lunch, dinner and two across the working day — suddenly an abstract number becomes five concrete checkpoints.
Frequently Asked Questions
What's the difference between hydration and water intake?
Hydration is the outcome — your body's fluid balance — while water intake is just one input. Your hydration status also depends on electrolytes, how much you sweat, and fluid from food and other drinks. This hydration calculator targets total daily fluid intake, which is the part you can actually control.
Can I drink too much water?
Yes, though it's rare in healthy people. Drinking several liters in a short window can dilute blood sodium (hyponatremia). Spread your goal across the whole day rather than chugging it at once, and increase intake gradually if you're increasing it at all.
How do I know if I'm well hydrated?
The simplest daily check is urine color: pale straw means you're on target, dark amber means drink more. Well-hydrated people also urinate roughly every 3–4 hours and rarely feel the dry-mouth thirst that signals mild dehydration has already set in.
Related Tools & Guides
Water Intake by Weight
Skip the form — see the full pound-by-pound and kilo-by-kilo chart.
How Much Water Should I Drink?
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Daily Water Intake Guide
What 'daily water intake' really covers — food, coffee and all.
Water Intake During Pregnancy
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Water Intake for Weight Loss
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Kids' Water Intake
Age-by-age hydration charts for children.