What this calculator does
Water needs depend on body weight, activity, climate and health. A common starting point for adults is 30–35 ml per kilogram of body weight.
This calculator adds exercise and climate allowances, then shows the result in litres and glasses. Kidney, heart or liver conditions may require a fluid restriction, so check with a clinician.
Water intake formula
Water (ml) = weight × 35 + (exercise minutes ÷ 30) × 350 + climate allowance Add 500 ml in hot weather and 1000 ml in very hot, humid conditions. Glass count depends on the glass size you choose.
How this calculator works
- 01
Enter weight and exercise
Use your body weight and average daily exercise minutes.
- 02
Select climate
Temperate, hot or very hot and humid — the allowance is added automatically.
- 03
Plan your intake
Spread the total across the day and use the glass count as a simple guide.
Frequently asked questions
How much water should I drink?
There is no universal number. For adults, 2–3 litres is a common guide, but weight, activity and climate matter more than a fixed target.
Do tea and coffee count?
Yes, they contribute to fluid intake. Water remains the simplest calorie-free option.
Can you drink too much water?
Very large amounts in a short time can disturb sodium balance. People with kidney or heart conditions should follow medical advice.
Data basis: 2026 · Annual constants live in structured JSON files and are updated once a year.
Results are unverified model calculations and do not replace tax, legal or financial advice.