How much water should I drink a day?
Water makes up around 60% of an adult’s body. It controls your temperature, carries nutrients, cushions your joints, keeps your bowels regular and helps your kidneys remove waste. Even mild dehydration — losing just 1–2% of body weight as fluid — can cause headaches, tiredness, poor concentration and constipation.
The European Food Safety Authority (EFSA) recommends a total water intake of about 2.0 litres a day for women and 2.5 litres for men, from drinks and food. But your real need depends on your size, activity and climate. In hot countries like the UAE, Saudi Arabia, Qatar and Pakistan you can lose much more through sweat. This water intake calculator gives you a personal target.
How the water intake calculator works
- Base need: 35 ml of fluid per kg of body weight (for example 70 kg × 35 = 2,450 ml).
- Exercise: + 500 ml for every hour of exercise, to replace sweat losses.
- Hot or humid climate: + 500 ml a day.
- Pregnancy: + 300 ml a day; breastfeeding: + 700 ml a day (EFSA).
Example: a 70 kg person who exercises 30 minutes a day in a hot climate needs about 2,450 + 250 + 500 = 3.2 litres a day.
Daily water intake chart: low, normal and high
| Daily fluid intake (adults) | Level | What it means |
|---|---|---|
| Under 1.5 litres | Low | Risk of dehydration, constipation, headaches and kidney stones |
| 1.5 – 3.5 litres | Normal | Healthy range for most adults, depending on size, activity and heat |
| 3.5 – 5 litres | High | Appropriate for large, very active people or heavy sweating; spread through the day |
| Over 5 litres (or over 1 litre per hour) | Very high | Risk of low blood sodium (hyponatraemia) unless medically advised |
Urine colour check
Pale straw or light yellow = well hydrated. Dark yellow or amber = drink more. Completely clear all day may mean you are drinking more than you need.
Benefits of drinking enough water
- More energy and focus — fatigue and “brain fog” are common signs of mild dehydration.
- Better digestion and fewer problems with constipation, especially when you eat more fibre (see the fibre calculator).
- Helps weight management: water before meals can reduce hunger, and replacing sugary drinks saves hundreds of calories.
- Kidney health: good hydration lowers the risk of kidney stones and urinary tract infections.
- Healthier skin and fewer headaches.
- Safer exercise in the heat and lower risk of heat exhaustion.
Health warnings
- People with heart failure, kidney disease or liver disease may be told to limit fluids — always follow your doctor’s advice.
- Drinking very large amounts quickly can cause hyponatraemia (low blood sodium), which can be dangerous. Do not drink more than about 1 litre per hour.
- In extreme heat or long workouts, water alone may not be enough — you may need electrolytes (salts).
- Older adults feel thirst less, so they should drink regularly even when not thirsty.
- Seek medical help for signs of severe dehydration: dizziness, confusion, very dark urine, or no urine for 8 hours.
Tips to drink more water
Keep a 1-litre bottle with you and aim to finish it by lunch. Drink a glass with every meal, flavour water with lemon, mint or cucumber, and eat water-rich foods such as watermelon, cucumber, oranges and yoghurt. Tea and coffee count too in moderation. During Ramadan, spread water between iftar and suhoor — our Ramadan nutrition guide explains how, and the fasting calculator helps you plan. Read more about the health benefits of drinking water.
Frequently asked questions
How much water should a woman drink a day?
Most women need about 2 litres of fluid a day from drinks, plus water from food. Pregnant women need about 300 ml more and breastfeeding women about 700 ml more. Hot weather and exercise increase needs further.
Is 3 litres of water a day too much?
For most healthy adults 3 litres is safe, especially in hot weather or with exercise. Spread it through the day rather than drinking large amounts at once.
Do tea and coffee count towards my water intake?
Yes. Tea, coffee, milk and laban all count. Caffeine has only a mild diuretic effect at normal amounts. Sugary drinks and juices count as fluid but add sugar and calories.
How much water should I drink in hot weather in the UAE?
In hot or humid conditions add at least 500 ml a day to your normal need, and more if you work outdoors or exercise. Drink before you feel thirsty and watch your urine colour.
Can drinking water help me lose weight?
Water has no calories, and drinking a glass before meals can help you feel fuller. Swapping one soft drink a day for water can save about 140 kcal.
How many glasses of water a day is that?
Divide your target in millilitres by 250 to get standard glasses. For example, 2.5 litres is about 10 glasses.
Sources
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on Dietary Reference Values for water. EFSA Journal 2010;8(3):1459.
- American College of Sports Medicine. Exercise and fluid replacement position stand. 2007.
- National Academies. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride and Sulfate. 2005.