How much water should I drink a day?
- 1Choose your sex and age group and enter your weight. Women can add pregnancy or breastfeeding.
- 2Enter how many minutes a day you exercise or do sweaty work.
- 3Pick the weather and the size of the glass you use.
- 4Read how much to drink in litres and glasses, the step-by-step working and the official reference amounts.
How is daily water intake calculated?
- 01Base water = weight kg × 35 ml (30 ml from 65)
- 02+ 0.6 L for each hour of exercise
- 03+ 0.5 L in warm weather, + 1.0 L in hot or humid weather
- 04+ 0.3 L in pregnancy, + 0.7 L when breastfeeding
- 05Drinks = total × 80 % (about 20 % comes from food) · Glasses = drinks ÷ glass size
A common rule used by doctors and dietitians is 30–35 ml of water per kg of body weight a day — about 1 ml for every calorie you burn. For a 70 kg adult that is about 2.5 litres, the same as the European Food Safety Authority's (EFSA) adequate intake for men (2.0 litres for women). Older adults are usually given about 30 ml per kg.
These amounts are for mild weather and light activity. Sweating raises your needs: the American College of Sports Medicine reports sweat losses of roughly 0.3–2.4 litres an hour, so the calculator adds a middle figure of 0.6 litres per hour of exercise, and 0.5–1 litre on warm or hot days. The WHO notes that people doing physical work in heat can need around 4.5 litres a day. If you sweat heavily, weigh yourself before and after exercise: each kilogram lost is about a litre to drink back.
EFSA adds 300 ml a day in pregnancy and 700 ml when breastfeeding. Food gives about a fifth of your water, so the amount to drink is about 80 % of the total.
A simple check: pale yellow urine means you are drinking enough; dark yellow means drink more.
Example: water for a 70 kg man
A man who weighs 70 kg and exercises for 30 minutes a day needs about 2.8 L of water a day.
About 0.5 L comes from food, so he should drink about 2.2 L — roughly 9 glasses of 250 ml.
Good to know
- Keep a bottle with you and refill it — it's the easiest way to drink enough.
- Drink a glass with each meal and one when you wake up; that is already 4 glasses.
- In summer heat and during Ramadan, drink steadily between iftar and sehri rather than a lot at once.
- Check your urine: pale yellow is good; dark yellow means drink more.
Water intake — common questions
How much water should I drink a day?
Most adults need about 2–2.5 litres of water a day in total, of which about 1.6–2 litres from drinks — around 8 glasses. You need more if you are heavier, exercise, live in a hot climate or are breastfeeding.
Pani kitna peena chahiye? (How much water should I drink?)
Aam taur par 8–10 glass (2–2.5 litre) roz. Garmi, exercise ya doodh pilane wali maaon ko zyada chahiye — upar apna wazan daal kar dekhein. (Usually 8–10 glasses a day; more in heat, with exercise or when breastfeeding.)
Do tea, milk and other drinks count?
Yes. Tea, coffee, milk, lassi, juice and soups all count towards your water. Water is still the best choice because it has no sugar or calories.
Is drinking too much water harmful?
It can be. Drinking many litres in a short time can lower the salt in your blood (hyponatraemia). Spread your water over the day and drink to thirst during long exercise.
How much water should I drink when pregnant or breastfeeding?
EFSA advises about 300 ml a day more in pregnancy (2.3 litres total) and 700 ml more when breastfeeding (2.7 litres total), including water from food.
How much water do I need in hot weather?
Add at least 0.5–1 litre on hot days, and more if you work or exercise outside. Drink before you feel very thirsty.
Sources
- EFSA Panel on Dietetic Products, Nutrition and Allergies – Scientific Opinion on Dietary Reference Values for water (EFSA Journal, 2010)
- US National Academies – Dietary Reference Intakes for Water, Potassium, Sodium, Chloride and Sulfate (2005)
- American College of Sports Medicine – Exercise and fluid replacement, position stand (Sawka et al., 2007)
- WHO – Domestic water quantity, service level and health (Howard & Bartram, 2003)
Formulas last reviewed: September 30, 2026 ·How we check our formulas