Daily water intake calculator
Estimate how much water your body needs each day based on your weight, physical activity level and climate. The calculation is for guidance only and runs locally in your browser.
How it works
Water needs vary widely from person to person depending on body weight, physical activity and climate. This tool applies a simple formula based on a ratio of milliliters per kilogram of body weight, adjusted for your activity level and the ambient heat.
Why does weight affect the result so much?
A heavier person has a larger blood volume and tissue mass, and therefore generally higher hydration needs. Most nutrition guidelines therefore use a per-kilogram ratio (usually between 30 and 40 ml/kg/day) rather than one fixed figure for everyone, like the famous "2 liters a day".
Does this estimate replace medical advice?
No. Some medical conditions (kidney or heart failure, pregnancy, breastfeeding, certain medications) significantly change the recommended water intake. This calculation gives an order of magnitude for a healthy person; if in doubt or if you have a specific condition, consult a healthcare professional.
Your personal data (weight, activity) never leaves your browser.