Water Intake Calculator

This calculator estimates how much water you should drink each day based on your body weight, how active you are, and how much you exercise, giving you a personal hydration target in both litres and glasses. The old advice of eight glasses a day is a rough one-size-fits-all rule that ignores the things that actually drive how much water you need, namely your size and how much you sweat. A larger body needs more water to function, and exercise, hot weather and physical work all increase losses through sweat that must be replaced. This tool tailors the number to you. The general guideline it uses is around 30 to 40 millilitres of water per kilogram of body weight per day, scaled by your activity level, plus an allowance for the fluid you lose during exercise. You enter your weight, choose an activity level from sedentary through to very active, and add your typical daily exercise in minutes, and the calculator returns your estimated daily water target in litres, the equivalent number of standard glasses, and your baseline need before exercise. Use it as a sensible starting point to build a hydration habit, to check whether you are drinking enough on active or hot days, or to set a goal in a drink-bottle you can track through the day. Remember that food, especially fruit and vegetables, provides some of your fluid, and that tea, coffee and milk count too, so not all of this needs to come from plain water. Thirst, and the colour of your urine, remain good everyday guides. This is a general wellness estimate, not medical advice; some health conditions require specific fluid limits, so follow your doctor's guidance where relevant.

A general guide only. Food and other drinks count toward fluid. Some health conditions need specific limits; follow your doctor's advice.