Water Intake Calculator

A common guideline is 35 ml per kilogram of body weight for a sedentary person in a temperate climate. Active people and those in hot weather need significantly more. For a 70 kg person with moderate activity, this is typically around 2.5–3 liters per day.

Yes — all beverages including coffee, tea, juices, and even food moisture count toward your daily fluid intake. However, alcohol has a diuretic effect and should not be counted.

Common signs include dark yellow urine, dry mouth, fatigue, dizziness, and headaches. Mild dehydration (1–2% of body weight) can already impair physical and cognitive performance.

Yes. During intense exercise you can lose 0.5–2 liters of fluid per hour through sweat. Drink 400–600 ml before exercise and replace fluids regularly during and after your workout. The activity level selector in this calculator already accounts for this.

Yes — overhydration (hyponatremia) occurs when excess water dilutes sodium in the blood, causing nausea, headache, confusion, and in severe cases, seizures. This is rare for most people in daily life but can occur in endurance athletes who drink large amounts of plain water without electrolyte replacement. For most healthy adults, the kidneys can process up to 0.8–1 liter per hour.

In hot weather or humid climates you can lose 1–2+ extra liters per day through sweat, even without exercise. In extreme heat (>35°C) or during outdoor work/sport, fluid needs can reach 5–8 liters per day. The "hot climate" option in this calculator adds approximately 500 ml to your base recommendation. High altitude also increases fluid losses through faster breathing.

Yes. Older adults are at higher risk of dehydration because the sense of thirst diminishes with age, and kidneys become less efficient at concentrating urine. People over 65 should consciously drink on a schedule rather than waiting for thirst. Children have higher water needs relative to body weight than adults. Pregnant and breastfeeding women need an additional 0.3–0.7 liters per day.

Use a marked reusable water bottle (500 ml or 1 liter) and set a goal to refill it a specific number of times. Set hourly reminders on your phone. Drink a glass of water with every meal and before bed. Eat hydrating foods — cucumber, watermelon, celery, and soups contribute 20–30% of daily fluid intake. Check urine colour: pale yellow (like lemonade) means adequate hydration; dark yellow means drink more.

Yes — carbonated (sparkling) water hydrates just as effectively as still water. The CO₂ does not significantly affect fluid absorption. However, flavoured sparkling waters may contain added acids or sweeteners. For dental health, limit sipping acidic beverages throughout the day and prefer still water for most of your intake.

Water can support weight loss in several ways: drinking 500 ml before meals reduces hunger and caloric intake by 13–22% in studies; water replaces high-calorie beverages; and adequate hydration supports metabolism and exercise performance. Some studies show that cold water may slightly increase metabolism as the body warms it, but the effect is small. Water itself has zero calories.