"Drink 8 glasses of water a day" is the most repeated health advice in the world – but it is not based on your body, your activity or the weather where you live. This guide explains how much water you should drink a day using the official guidelines, a simple water intake formula based on body weight, and the extra you need for exercise, hot weather, pregnancy and breastfeeding.
Why Water Matters
Water makes up roughly 50%–60% of an adult's body weight. It regulates body temperature through sweat, carries nutrients and oxygen to cells, cushions joints, keeps digestion moving and helps the kidneys remove waste. You lose water all day through breathing, sweating and urine, so it must be replaced every day. Even mild dehydration – losing 1%–2% of body weight as water – can cause headache, tiredness, poor concentration and constipation.
Daily Water Intake Guidelines
Health authorities give adequate intake figures for total water – from drinks and food. About 20% of our water usually comes from food such as fruit, vegetables, dal, curd and rice.
| Source | Men (total water) | Women (total water) |
|---|---|---|
| European Food Safety Authority (EFSA) | 2.5 litres a day | 2.0 litres a day |
| US National Academies | 3.7 litres a day | 2.7 litres a day |
Taking away the share from food, that means roughly 2 to 3 litres of drinks a day for men and 1.6 to 2.2 litres for women in a temperate climate with light activity. In a hot Indian summer, you will need more.
Water Intake Formula by Body Weight
A simple rule used by many dietitians is:
Daily water (litres) = body weight (kg) × 0.033
That is about 33 ml of water per kilogram of body weight. Some clinicians use a range of 30–35 ml per kg.
| Body weight | Base daily water (33 ml/kg) | About how many glasses (250 ml) |
|---|---|---|
| 50 kg | 1.65 litres | 6–7 glasses |
| 60 kg | 2.0 litres | 8 glasses |
| 70 kg | 2.3 litres | 9 glasses |
| 80 kg | 2.6 litres | 10–11 glasses |
| 90 kg | 3.0 litres | 12 glasses |
So, how much water should I drink according to my weight? A 70 kg adult needs roughly 2.3 litres a day as a starting point, before adding for exercise and heat.
Extra Water for Exercise
When you exercise you sweat, and sweat losses vary widely – from under 0.5 litres to more than 2 litres per hour in hot conditions. A practical guide is to drink an extra 400–800 ml for every hour of exercise, sipping before, during and after. For intense sessions longer than an hour, or heavy sweating in the heat, a drink with electrolytes (sodium and potassium) helps replace what you lose. A simple home option is water with a pinch of salt and some lemon and sugar, or oral rehydration solution (ORS).
Hot Weather and Water Intake
In Indian summers, when temperatures cross 35–40°C, you can lose a lot of water through sweat even without exercise. Increase your intake by about 500 ml to 1 litre a day in hot weather, and more if you work outdoors. Buttermilk (chaas), coconut water, nimbu pani and fruits like watermelon and cucumber all count towards your total and help replace salts. Watch out for signs of heat exhaustion – heavy sweating, dizziness, nausea and a fast pulse – and move to a cool place and drink fluids immediately.
Water Intake During Pregnancy and Breastfeeding
Needs rise during pregnancy and even more while breastfeeding. EFSA recommends an extra 300 ml a day in pregnancy and about 700 ml a day while breastfeeding, on top of the normal intake for women. Follow your doctor's advice, especially if you have swelling, high blood pressure or kidney problems. Track your pregnancy week by week with our pregnancy calculator.
Signs You Are Drinking Enough – or Not
Signs of good hydration
- Urine that is pale yellow, like lemonade.
- Rarely feeling very thirsty.
- Urinating every 3–4 hours during the day.
Signs of dehydration
- Dark yellow or amber urine, and urinating less often.
- Thirst, dry mouth and lips.
- Headache, tiredness or dizziness.
- Constipation.
Older adults feel thirst less strongly, so they should drink regularly rather than waiting to feel thirsty. Children and elderly people become dehydrated faster during diarrhoea, vomiting or fever – ORS is the first treatment.
Can You Drink Too Much Water?
Yes, although it is rare in healthy people. Drinking very large amounts in a short time – several litres within a few hours – can dilute the sodium in your blood, a dangerous condition called hyponatraemia (water intoxication). It has occurred in endurance athletes and in water-drinking challenges. The kidneys can handle about 0.8–1 litre an hour, so spread your drinking through the day. People with heart failure or kidney disease may be told to limit fluids – always follow your doctor's advice.
Does Tea, Coffee or Food Count?
Yes. Tea, coffee, milk, buttermilk, soups and water-rich foods all count towards your daily water intake. Moderate amounts of tea and coffee do not dehydrate you overall, although their caffeine has a mild diuretic effect. Sugary drinks, packaged juices and alcohol are not good ways to hydrate – they add calories and, in the case of alcohol, increase fluid loss.
Easy Ways to Drink More Water
- Start the day with a glass of water.
- Keep a bottle on your desk and refill it at fixed times.
- Drink a glass with every meal and snack.
- Flavour water naturally with lemon, mint, cucumber or tulsi.
- Eat water-rich foods – watermelon, cucumber, oranges, tomatoes, curd.
- Use reminders on your phone if you tend to forget.
Water Needs for Children and Older Adults
Children need less water in total but more per kilogram of body weight than adults, and they dehydrate faster during play, illness and hot weather. As a rough guide, EFSA suggests a total water intake of about 1.1–1.3 litres a day for children aged 2–8, rising to adult levels in the teenage years. Encourage children to drink water with every meal and after play, and avoid sugary drinks. Older adults often feel less thirsty and may drink too little, which increases the risk of urine infections, constipation and confusion. A simple routine – a glass of water at fixed times and with each medicine – helps.
Best Times to Drink Water
- After waking up – you lose water overnight through breathing.
- About 30 minutes before meals – it can help with digestion and portion control.
- Before, during and after exercise.
- When you feel tired or have a headache – mild dehydration is a common cause.
- Less in the hour before bed if waking up at night to urinate bothers you.
Water Myths and Facts
- "Clear urine is the goal." Completely clear urine can mean you are drinking more than you need. Pale yellow is ideal.
- "You must drink only plain water." Milk, buttermilk, tea, soups and fruit all count.
- "Thirst means you are already badly dehydrated." For healthy adults, thirst is an early and reliable signal – just respond to it.
Frequently Asked Questions
How much water should I drink a day?
About 33 ml per kg of body weight is a good starting point – roughly 2.3 litres for a 70 kg adult – plus extra for exercise and hot weather. Guidelines suggest a total water intake (from drinks and food) of about 2.5 to 3.7 litres for men and 2 to 2.7 litres for women.
Is 8 glasses of water a day enough?
Eight 250 ml glasses equal 2 litres, which is reasonable for many women and lighter adults in mild weather. Heavier people, active people and anyone in hot weather usually need more.
How much water should I drink according to my weight?
Multiply your weight in kg by 0.033. For example, 60 kg × 0.033 = about 2 litres a day.
How much extra water do I need when exercising?
Roughly 400 to 800 ml for every hour of exercise, more in hot weather or if you sweat heavily.
How can I tell if I am dehydrated?
Dark yellow urine, urinating less often, thirst, dry mouth, headache and tiredness are common signs. Pale yellow urine usually means you are well hydrated.
Does tea or coffee count as water intake?
Yes. In moderate amounts tea and coffee count towards your daily fluids, as do milk, buttermilk, soups and water-rich foods.
Is it bad to drink water while eating?
No. Drinking water with meals is safe for most people and can help digestion. It does not dilute stomach acid enough to cause problems.
Does drinking water help with weight loss?
It can help a little. Water has no calories, replacing sugary drinks with water cuts calories, and drinking a glass before meals may help some people eat less.
How many litres of water should a woman drink a day?
About 1.6 to 2.2 litres from drinks for most women in mild weather, plus more in hot weather, during exercise, pregnancy and breastfeeding.
Disclaimer: These are general guidelines for healthy adults. People with kidney, heart or liver disease, or who are pregnant or breastfeeding, should follow their doctor's advice on fluid intake.