Water Intake Calculator

“Eight glasses a day” is easy to remember but does not fit everyone. Needs vary with body weight, how much you sweat and the weather — a 90 kg person and a 55 kg person cannot need the same.

The calculator applies a widely used rule of thumb: about 33 ml per kg of body weight, plus 350 ml for every half hour of exercise and half a litre in hot or humid weather.

How to calculate Water intake

1. Enter your weight.
2. Enter how many minutes you exercise on an average day.
3. Choose whether the weather is hot or humid; read the result in litres and glasses.

Water intake formula

• Water (ml) = weight (kg) × 33
• + 350 ml for every 30 minutes of exercise
• + 500 ml in hot or humid weather

Water intake example

For someone weighing 70 kg who exercises 30 minutes a day: 70 × 33 = 2,310 ml, plus 350 ml for exercise gives 2,660 ml — about 2.7 litres or 11 glasses.

Water intake: common questions