Water Intake Calculator – Free Online

About this calculator

A general rule is about 35 ml of fluid per kilogram of body weight, plus extra for exercise and hot weather. Needs vary, and food and other drinks also contribute.

The formula

Daily water ≈ 35 ml × kg + 12 ml × exercise minutes (+ 500 ml in hot climates)

Worked example70 kg, 30 min exercise, temperate → 2,450 + 360 = 2.8 litres.

Frequently asked questions

Does coffee count?

Yes, tea and coffee contribute to your fluid intake, as does water in food.

Can I drink too much?

Excessive amounts in a short time can be harmful. Spread intake across the day.

Should I follow this exactly?

Treat it as a starting point. Thirst and urine colour are good guides; medical conditions change needs.