Quick answers to the most common hydration questions. For deeper dives, check the blog or tools.
It depends on your body weight, climate, and activity level. A general baseline is 30–35 mL per kg of body weight. Use our Daily Water Intake Calculator for a personalized goal.
No. Coffee has a Beverage Hydration Index of about 0.98, meaning it hydrates almost as well as water. The diuretic effect of moderate caffeine is small and does not cause net fluid loss.
The BHI measures how much fluid your body retains from a drink compared to plain water. Milk scores 1.5, sports drinks 0.95–1.0, and beer 0.79. Try our Beverage Hydration Index Tool.
Signs include white salt stains on clothes, stinging eyes when you sweat, frequent cramping, and salt cravings after exercise. You can also do a sweat sodium patch test. Our Exercise Sweat Loss Estimator can help.
No. The "8 glasses" rule is a misinterpretation of a 1945 recommendation that included water from food. Your actual needs depend on weight, climate, and activity.
No. All calculations run entirely in your browser. We never see your weight, activity level, or health information.