Find out exactly how much water your body needs each day — personalized for your weight, activity level, climate, and life stage.
Sedentary baseline — minimum for organ function and cellular hydration.
Hard daily exercise significantly increases sweat-based fluid losses.
Twice-daily training demands the highest baseline hydration support.
Heat and humidity increase evaporative losses through sweat.
Extra fluids support increased blood volume and amniotic fluid.
Milk production requires significant additional daily fluid intake.
General guidance from health authorities suggests 2–3.5 liters per day for most adults, but the right amount varies considerably with body weight, activity level, and climate. A common and well-supported approach is drinking roughly 35–40 ml per kilogram of body weight for sedentary to lightly active individuals. This calculator gives you a personalized estimate based on your specific inputs.
Yes, mostly. Despite the myth, caffeinated beverages like coffee and tea do contribute to your daily fluid intake. Studies show that moderate caffeine consumption (up to 400 mg/day) does not cause net fluid loss. However, very high caffeine intake can have a mild diuretic effect, so plain water remains the gold standard for hydration.
The simplest indicator is urine color. Pale straw-yellow urine indicates good hydration, while dark yellow or amber urine is a sign you need more fluids. Other signs of dehydration include fatigue, headaches, reduced concentration, dry mouth, and decreased physical performance. Thirst is actually a late-stage dehydration signal — by the time you feel thirsty, you may already be 1–2% dehydrated.
Yes, significantly. You can lose 0.5–2 liters of water per hour during intense exercise through sweat, depending on intensity, temperature, and individual variation. Sports medicine guidelines recommend drinking 400–800 ml per hour of exercise, with additional electrolytes for sessions over 60 minutes. This calculator uses activity level to account for increased baseline needs, but add extra intake on specific workout days.
HC Webhook sends your health data — including hydration logs from Apple Health — to any endpoint on a schedule, keeping your wellness stack always up to date.
