Daily Water Intake Calculator
A common baseline is 30–35 ml of water per kilogram of body weight per day, plus more for exercise and hot weather. A 70 kg adult with 30 minutes of exercise in a temperate climate needs roughly 2.8 litres a day.
Daily water target
2.8 L
About
11.8 cups
Show the math
- 1
Start from your body weight
70 kg × 35 ml = 2,450 ml
A commonly used baseline is about 30–35 ml of water per kilogram of body weight per day.
= 2,450 ml
Read the steps as text
- Start from your body weight. 70 kg × 35 ml = 2,450 ml A commonly used baseline is about 30–35 ml of water per kilogram of body weight per day.
- Add extra for exercise. 30 min ÷ 30 × 350 ml = 350 ml Sweat losses during activity add to your baseline needs — roughly 350 ml per 30 minutes of exercise.
- Add extra for a hot climate. + 0 ml (temperate climate) Heat and humidity increase fluid loss through sweat, even without exercise.
- Add it all up. 2,450 + 350 + 0 = 2,800 ml
Where the baseline comes from
There's no single universally 'correct' daily water target — needs vary with body size, activity, climate, diet and individual physiology. A commonly cited baseline used by dietitians is about 30–35 ml per kilogram of body weight per day, which this calculator uses as its starting point before adding exercise and climate adjustments.
This is water from all sources combined — drinks, and the roughly 20% that typically comes from food — not necessarily 30–35 ml that has to come from plain water alone.
Adjusting for exercise and heat
Sweat losses during exercise need replacing on top of your baseline; this calculator adds roughly 350 ml for every 30 minutes of activity, a common rule of thumb, though heavy sweaters may need more. A hot or humid climate increases fluid loss through sweat even without exercise, so it adds a flat extra amount as well.
Thirst, urine colour (pale yellow is a good sign) and how you feel are more reliable day-to-day guides than any fixed number — treat this calculator's result as a starting point to adjust from, not a strict requirement.
Frequently asked questions
- How much water should I drink a day?
- A common guideline is 30–35 ml per kilogram of body weight, plus more for exercise and hot weather — enter your numbers above for a personalised estimate.
- Does this include water from food and other drinks?
- Yes, this is a total daily fluid target from all sources — food typically supplies around 20% of daily water intake, with drinks making up the rest.
- Can I drink too much water?
- Yes, though it's uncommon — drinking far more than your body can process can dilute sodium levels dangerously (hyponatremia). This mostly affects endurance athletes drinking excessively during long events, not everyday intake.