Calculate how much water you should drink daily based on your body weight and activity level. Stay hydrated with personalized recommendations.
The "8 glasses of water a day" rule is a simple guideline but not perfect. Individual needs vary based on weight, activity, climate, and diet. This calculator uses weight-based formulas (0.5 oz per pound of body weight) adjusted by activity, which is more personalized than a one-size-fits-all rule.
Yes. During and after exercise, you lose fluids through sweat. Add 7–10 oz extra for every 10–20 minutes of intense exercise. This calculator's "Active" and "Very Active" levels account for this, but on high-heat days or intense workouts, drink more.
Yes—hyponatremia (water intoxication) is rare but possible from excessive water intake without electrolyte replacement, especially during endurance events. For normal daily hydration, drinking to thirst and checking urine color (pale yellow = well-hydrated) is safer than over-drinking.
Mostly yes, but caffeine has a mild diuretic effect. Plain water is the best choice. If you drink caffeinated beverages, count them at 50–75% of their volume toward your daily water goal. Avoid sugary drinks—they add calories without hydration benefits.
Water regulates body temperature, transports nutrients, cushions joints, aids digestion, and supports cognitive function. Dehydration causes fatigue, headaches, reduced performance, and poor focus. Proper hydration is crucial for physical activity, health, and mental clarity.