Water Intake by Body Weight
Calculate your hydration target proportional to your body weight using the most common formula.
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This is a starting baseline. Add 300-600ml per 30 minutes of exercise, and more in hot weather. This does not account for water from food (usually about 20% of total intake).
How the Water Intake by Body Weight Works
The Water Intake by Body Weight estimates your daily fluid needs using your body weight as a base (approximately 35 ml/kg/day for adults), then adjusts upward based on activity level, climate exposure, and other hydration factors. Research shows that hydration needs can vary by 2x or more between sedentary and highly active individuals.
The result is a total daily fluid target from all sources — including food, which contributes roughly 20% of total fluid intake for most people. The "drink" target shown accounts for the food contribution.
Frequently Asked Questions
How is my water intake target calculated?
Water needs are estimated using your body weight as a baseline (approximately 35 ml per kg per day) adjusted for activity level, climate, and other factors. Research shows hydration needs vary considerably between individuals based on these variables.
Does coffee or tea count toward my daily fluid intake?
Yes — contrary to the old myth, caffeinated drinks like coffee and tea contribute to your daily fluid intake. However, alcohol is dehydrating and should not be counted. Water and non-caffeinated drinks remain the most efficient sources of hydration.
How can I tell if I'm adequately hydrated?
Urine colour is one of the most reliable real-world indicators. Pale yellow (like lemonade) suggests good hydration. Dark yellow or amber signals you need more fluids. Clear urine may indicate overhydration, which can dilute important electrolytes.
Does exercise affect my hydration needs?
Significantly. During moderate exercise, you can lose 0.5–2 litres of sweat per hour depending on intensity and conditions. The calculator accounts for activity level. For endurance sports over 60 minutes, electrolyte replacement alongside water is also recommended.
Is it possible to drink too much water?
Yes — overhydration (hyponatremia) can dilute blood sodium to dangerous levels. This is rare in everyday life but a real risk for endurance athletes who drink plain water in excess without replacing electrolytes. Use the target as a guide, not a minimum to maximise.