About this calculator
This uses a common rule of thumb: about 35 ml of water per kilogram of body weight, plus about 350 ml for every 30 minutes of exercise. It is a starting point, not a prescription.
Worked example
At 70 kg with 30 minutes of exercise: 70 × 35 ml + 350 ml = about 2.8 litres a day.
How to use the water intake calculator
- Enter the weight.
- Enter the exercise per day.
- Read the result — it updates as you type.
Frequently asked questions
Does tea or coffee count?
Most drinks contribute to your daily fluid intake, and so does water in food.
Should I drink more in hot weather?
Yes. Heat and sweating increase how much you need.