How Much Water Should You Drink a Day? By Weight, Exercise and Weather

"Drink 8 glasses a day" is easy to remember, but it's only an average. A 50 kg office worker in Shimla and an 85 kg delivery rider in Chennai in May need very different amounts. A better starting point is your body weight, adjusted for exercise and heat.

The simple rule: 35 ml per kg

Water from drinks (ml) ≈ weight (kg) × 35

Then add about:

• 12 ml for every minute of exercise (roughly 350 ml per half hour)
• 500 ml in hot or humid weather, which covers much of India for much of the year
• 300 ml when pregnant and 700 ml when breastfeeding

Example: 70 kg, 45 minutes of exercise, Indian summer: 70 × 35 + 45 × 12 + 500 = 3,490 ml, about 3.5 L or 14 glasses.

Daily water by weight

What counts as water?

Tea, milk, buttermilk, nimbu pani, coconut water and soups all count. So do water-rich foods: dal, curd, fruit and vegetables supply about 20% of the water you take in. European food-safety advice puts total water (food plus drinks) at about 2.0 litres a day for women and 2.5 litres for men in a mild climate, which matches the rule above.

Tea and coffee in normal amounts still hydrate you overall. Sugary drinks and juices count as water but add calories, so plain water should be most of it.

How to tell you're drinking enough

• Urine colour: pale straw yellow is good. Dark yellow means drink more.
• Thirst: if you're often thirsty, you're behind.
• Warning signs of dehydration: headache, tiredness, dizziness, dry mouth and cramps, especially in summer.

Tips that work

• Keep a 1-litre bottle at your desk and aim to finish it by lunch and again by evening.
• Drink a glass with every meal and before and after exercise.
• In heavy sweating, add a pinch of salt and sugar or drink ORS to replace lost salts.

Watching your weight as well? Pair this with the calorie calculator.