Water Intake Calculator
A common rule is about 35 ml of water per kilo of body weight a day, plus more for exercise and heat. This calculator applies that rule to you.
How it works
Daily water (ml) = weight (kg) × 35 + exercise minutes ÷ 30 × 500 + 500 if hot/humid. The 35 ml/kg rule sits inside the commonly advised 30–40 ml/kg range for adults.
Examples: 70 kg, no exercise, moderate climate: 70 × 35 = 2,450 ml = 2.45 litres (9.8 glasses). Same person with 60 minutes of exercise: 2,450 + 1,000 = 3.45 litres. Hot climate adds 500 ml.
Frequently asked questions
Is the 8-glasses rule wrong?
It is a rough average that happens to fit a 55–60 kg adult. Heavier people and active people need more; this calculator scales with weight.
Does food count?
Yes — food typically supplies around a fifth of daily water. This calculator gives total water need; drinking the full amount on top of food is still safe for most people.
Can I drink too much?
Yes, though it is rare: very large intakes in a short time can dilute blood sodium. Spread intake through the day rather than chugging litres at once.
Do coffee and tea count?
Mostly yes — caffeinated drinks still hydrate, despite the mild diuretic effect. They count toward the total.