Why your body needs water
Water makes up about 60% of an adult's body weight and is essential to almost every function: regulating temperature, carrying nutrients and oxygen to cells, flushing waste, cushioning joints and keeping your brain sharp. Even mild dehydration of 1–2% can cause headaches, fatigue and poor concentration.
How we calculate your needs
- Baseline: about 33 ml per kilogram of body weight per day.
- Exercise: about 350 ml extra for every 30 minutes of activity.
- Hot weather: an extra 0.5–1 liter to replace sweat.
- Pregnancy and breastfeeding: roughly 300 ml and 700 ml extra respectively.
Example: a 70 kg person who exercises 30 minutes in a temperate climate needs about 2.7 liters a day — roughly 11 cups. This includes water from food and other drinks; fruit and vegetables provide around 20% of your intake.
Hydration while fasting
During Ramadan, drinking is limited to the hours between iftar and suhoor. Tick “Fasting” to get a schedule spread across those hours. Avoid gulping large amounts at once, limit coffee, tea and soft drinks, and eat water-rich foods like cucumber and watermelon at suhoor.
Signs you're not drinking enough
- Dark yellow urine (pale yellow is ideal).
- Dry mouth and lips, constant thirst.
- Headaches, tiredness and poor focus.
- Constipation and infrequent urination.
Tips to drink more
- Carry a reusable water bottle.
- Drink a glass when you wake up and before each meal.
- Add lemon or mint if you dislike plain water.
- Use the Pomodoro Timer to remind you to drink at every break.
⚕️ People with heart or kidney conditions may need to limit fluids — follow your doctor's advice.
Frequently Asked Questions
How much water should I drink a day?
Most adults need 2–3 liters a day; the exact amount depends on weight, activity and climate, which this tool calculates.
Do tea and coffee count?
They contribute to hydration, but caffeine is mildly diuretic, so make water your main source.
Can I drink too much water?
Yes — drinking very large amounts in a short time can cause low sodium, so spread intake through the day.
How should I hydrate during Ramadan?
Tick “Fasting” for a schedule between iftar and suhoor and drink small amounts frequently.
Do athletes need more water?
Yes. Drink before, during and after training, and replace electrolytes in long sessions.
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