How much water should you drink a day?

Steps

1. Multiply your weight in kilograms by 35 to get millilitres: 70 × 35 = 2,450 ml.
2. Add 350 ml for each 30 minutes of exercise you do in a day: 350 ml for 30 minutes.
3. Add them: 2,800 ml, which is 2.8 litres.
4. Divide by 250 ml to get glasses: about 11.
5. Or enter your weight and exercise minutes in the water intake calculator.

Examples

A person weighing 60 kg who does no exercise gets 2.1 litres, about 8 glasses. A person weighing 80 kg who exercises for an hour gets 80 × 35 + 700 = 3,500 ml, or 3.5 litres, about 14 glasses.

The target counts all drinks, and many foods such as fruit, vegetables and soup contribute water too, so you do not need to drink the whole figure as plain water.

What changes your need

Hot weather, high altitude, illness with fever or diarrhoea, pregnancy and breastfeeding raise the need. Thirst and the colour of your urine are good everyday signs: pale yellow usually means enough. Drinking far more than you need is not helpful and in rare cases is harmful.

Medical conditions

Some conditions, including certain heart, kidney and liver problems, require limiting fluids, and a doctor’s advice then overrides any formula. The result here is a general estimate for a healthy adult, not medical advice.