How much water should you drink a day?

The short answer

For most healthy adults, about 6 to 8 glasses of fluid a day is a sensible everyday guide — a glass being about 250 ml — with more in hot weather or when you’re active. India’s National Institute of Nutrition (ICMR–NIN) puts it at about eight glasses, or roughly two litres, of water including other drinks. The UK’s NHS says 6 to 8 cups or glasses a day.

Then check yourself: if your pee is pale and you’re rarely thirsty, you’re very likely getting enough.

What the official guidance says

• India (ICMR–NIN, 2024): “about eight glasses (approximately two litres) of water including beverages per day”, and more during very hot weather or vigorous physical activity.
• UK (NHS): 6 to 8 cups or glasses of fluid a day. Water, lower-fat milk and sugar-free drinks, including tea and coffee, all count.
• US (National Academies, 2004): about 2.7 litres a day of total water for women and 3.7 litres for men — from all drinks and foods. About 20% usually comes from food.
• Europe (EFSA, 2010): 2.0 litres a day of total water for women and 2.5 litres for men, including the water in food, at moderate temperatures and activity levels.

The American and European figures look bigger because they count all the water you take in, including the water in your food — around a fifth of it — rather than how many glasses to drink. Mayo Clinic’s summary gives the same range for the average healthy adult: about 2.7 to 3.7 litres of total fluid a day, with about 20% from food.

Is “8 glasses a day” a myth?

Partly. A well-known 2002 review found no scientific studies supporting the “8 × 8” rule — eight 8-ounce glasses a day — for healthy adults in a temperate climate who aren’t very active. The US National Academies deliberately gave no glasses-per-day rule of thumb, and said most healthy people meet their needs by letting thirst be their guide.

Still, both India’s guidelines and the NHS use about eight glasses as a practical target. Treat it as a starting point, not a rule: you’ll need more on a hot day or after exercise.

Do tea and coffee count?

Day to day, yes. The NHS counts tea and coffee, and a 2014 study of regular coffee drinkers found that moderate coffee intake hydrated about as well as water. India’s dietary guidelines suggest keeping caffeine under 300 mg a day.

The exception is when you’re already dehydrated, or it’s very hot. The NHS advises avoiding caffeinated drinks and alcohol when you’re dehydrated, and India’s heatwave advisory lists tea, coffee, alcohol and fizzy or very sugary drinks among the things to avoid. Then water, oral rehydration solution (ORS), lemon water or buttermilk are the better choices.

How to tell if you’re drinking enough

• Look at the colour of your pee. The NHS advises drinking enough during the day that your pee is pale. Mayo Clinic describes colourless or light yellow as the sign you’re getting enough; dark yellow means drink more.
• Listen to thirst — except in a heatwave. For most healthy people, thirst works well. But in extreme heat, India’s health ministry warns that thirst is not a good indicator of dehydration: drink regularly anyway.

Can you drink too much?

It’s rare, but yes. Drinking far more than your body needs can dilute the sodium in your blood — a condition called hyponatremia, which can be life-threatening. There’s no benefit in forcing down litres beyond what keeps your pee pale. Even for people doing hard physical work in the heat, US workplace-safety guidance (NIOSH) caps it at about 1.4 litres an hour.

Making it easy

The simplest routine is to spread it out: a glass when you wake up, one with each meal, and one or two in between. If a busy workday swallows the in-betweens, try these 8 habits for drinking more water at work.