Water Intake Calculator - How Much Water Should You Drink a Day?

There is no single number that suits everyone. A 50 kg office worker in Bengaluru and a 90 kg construction worker in Delhi in May need very different amounts. That is why this calculator starts from your body weight instead of a fixed rule.

The old advice of "8 glasses a day" (about 2 litres) is a reasonable starting point for a smaller adult, but it is not based on your size, activity or weather. The 35 ml per kg method scales with you, so larger and more active people get a higher target and smaller people are not pushed to drink more than they need.

The calculator adds up three parts to estimate how much water you should drink a day:

For example, a 65 kg person who walks briskly for 30 minutes on a hot day needs about 2,275 + 300 + 500 = 3,075 ml, or roughly 3.1 litres (12 glasses). The result is shown in litres, 250 ml glasses and, if you enter your weight in pounds, US fluid ounces.

When temperatures cross 35°C, or when humidity is high in cities like Chennai, Mumbai or Kolkata, you sweat more even while sitting still. Most people need about 500 ml to 1 litre more water a day in these conditions, and more if they work outdoors.

You can lose 0.5 to 1 litre of sweat an hour during exercise, and more in the heat. The calculator adds 300 ml for every 30 minutes, which covers most gym sessions, runs and sports for most people.

• Before: drink a glass of water in the 1-2 hours before you work out.
• During: take a few sips every 15-20 minutes for sessions longer than 30 minutes.
• After: drink to thirst. Pale yellow urine a couple of hours later means you have caught up.

For workouts longer than an hour, or heavy sweating in the heat, a drink with some sodium (ORS, salted chaas or a sports drink) helps more than plain water alone. Want to know what your workout burned? Try the Calories Burned Calculator.

Yes. Tea and coffee are mostly water. Caffeine has a mild diuretic effect, but at normal amounts (3-4 cups a day) you still keep most of the fluid. Here is how common drinks and foods compare:

Your body gives clear signals. Pale yellow urine through the day is the simplest sign you are drinking enough.

Drinking far too much water in a short time can dilute the sodium in your blood, a condition called hyponatremia. It is rare in healthy people and usually happens only when someone drinks several litres within a few hours, for example during very long endurance events. Spread your water through the day and you are very unlikely to have a problem.

Water has no calories, and swapping sugary drinks, sweet chai or packaged juice for water is one of the easiest ways to cut calories without feeling deprived. Drinking a glass of water before meals may also help some people feel full sooner.

Water on its own does not burn fat, though. Weight loss still comes down to eating fewer calories than you burn. Our guide on the role of hydration in weight loss explains the details.