HomeHealth
Water intake calculator
A daily water target from your weight and exercise.
Quick answer
A rule of thumb for water intake is 35 ml per kg of body weight, plus extra for exercise. Formula: Water (ml) = weight in kg ร 35 + 350 ml for every 30 minutes of exercise. A 70 kg person who exercises 30 minutes a day is looking at about 2.8 litres of fluids.
Read the guide: How to calculate your daily calories (TDEE)
Daily water target
2.80
- In glasses of 250 ml
- 11
Litres, counting all drinks. Hot weather, illness and pregnancy raise needs; some medical conditions limit fluids. A general estimate, not medical advice. Talk to a doctor or dietitian about your own health.
How is daily water intake calculated?
A common rule of thumb is about 35 ml of fluid for each kilogram of body weight, with extra for exercise and heat.
Food, tea and other drinks count towards the total, not only plain water.
Pale yellow urine and not feeling thirsty are the simplest signs you are drinking enough.
What is the formula for daily water intake?
- Water (ml) = weight in kg ร 35 + 350 ml for every 30 minutes of exercise
- Divide by 1,000 for litres
Can you show a worked example of daily water intake?
70 kg ร 35 = 2,450 ml, plus 350 ml for 30 minutes of exercise = 2,800 ml, which is 2.8 litres or about 11 glasses.
How much water should I drink for my weight?
Litres a day, counting all drinks. A general estimate, not medical advice.
| Weight | No exercise | 30 min exercise | 60 min exercise |
|---|---|---|---|
| 40 kg | 1.4 L | 1.8 L | 2.1 L |
| 50 kg | 1.8 L | 2.1 L | 2.5 L |
| 60 kg | 2.1 L | 2.5 L | 2.8 L |
| 70 kg | 2.5 L | 2.8 L | 3.1 L |
| 80 kg | 2.8 L | 3.1 L | 3.5 L |
| 90 kg | 3.1 L | 3.5 L | 3.9 L |
Common questions
Do I really need eight glasses a day?
The eight-glasses rule is a rough habit, not a law. Your size, climate and activity set your real need.
Does tea or coffee count?
Yes, they count towards fluid intake.
Can you drink too much water?
Yes, though it is rare. Very large amounts in a short time can be dangerous. Drink steadily through the day.
Does hot weather change it?
Yes. Sweating raises your need, so add extra on hot days or when you are ill.