Water Intake Calculator

The Water Intake Calculator estimates how much fluid you should drink per day from three factors: body weight, activity level, and climate. The baseline rule of thumb is about 33 millilitres per kilogram of body weight - roughly 2.3 litres for a 70 kg adult - before adjustments.

The adjustments matter because fluid needs swing widely around the baseline. Activity multiplies need up as sweat losses grow: light exercise nudges the figure up about 20 percent, while heavy daily training adds 60 percent or more. Climate adjusts for the environment - hot or humid conditions raise the target, while cold climates slightly lower it because respiratory and sweat losses fall. The tool also converts the result into 250 ml glasses, which is the unit people actually pour.

Treat the output as a daily target to approach across the day rather than a quota to chug; spreading intake aids absorption and sleep (front-loading fluids means night trips). Foods contribute too - fruit, soups, and coffee all count toward hydration despite the myths. Thirst, urine colour, and energy remain the best real-time indicators.

Medical conditions such as kidney or heart disease change fluid requirements substantially, so follow clinician guidance where it exists. Calculation is instant and local to your browser.