How we estimate your water needs
- Base: 35 ml for every kg of body weight.
- Exercise: add about 350 ml for every 30 minutes.
- Hot or humid weather: add about 500 ml.
- Pregnancy: add 300 ml; breastfeeding: add 700 ml (EFSA).
The European Food Safety Authority sets adequate total water intake at 2.5 litres a day for men and 2.0 litres for women, from food and drinks together.
Signs you need more water
- Dark yellow urine or passing urine rarely
- Thirst, dry mouth or headache
- Tiredness or dizziness, especially in summer
Tips to drink enough
- Keep a 1-litre bottle with you and refill it twice.
- Drink a glass with every meal.
- Nimbu pani (without much sugar), buttermilk and coconut water also count.
Frequently asked questions
Are 8 glasses of water a day enough?
Eight 250 ml glasses is 2 litres, which suits many smaller adults. Larger, active people or those in hot weather need more.
Do tea and coffee count?
Yes. They still hydrate you overall, though very strong coffee in large amounts can make you pass more urine.
Can I drink too much water?
Yes, though it is rare. Drinking many litres in a short time can lower blood sodium. Spread your water through the day.
Should people with kidney or heart disease follow this?
No. They should follow the fluid limit their doctor gives them.
Sources
- European Food Safety Authority. Scientific opinion on dietary reference values for water. EFSA Journal, 2010. Link
- ICMR – National Institute of Nutrition, Hyderabad. Dietary Guidelines for Indians and Nutrient Requirements (RDA) 2020. Link
Medical disclaimer: This calculator gives estimates for general information only. It is not a diagnosis or a substitute for advice from a doctor or registered dietitian. Please consult a healthcare professional before making changes to your diet, exercise or medicines, especially if you are pregnant, have a medical condition or take regular medication.
Last updated: 20 October 2026. Read our editorial policy.
