Water Intake Calculator
Find your recommended daily water intake based on weight and activity.
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Water Intake Calculator
Use the formula and worked example below to calculate manually.
Overview
The water intake calculator estimates how much water you should drink daily based on your body weight, activity level, and climate — to maintain optimal hydration.
How to use this calculator
- Enter your body weight.
- Select your activity level.
- Optionally indicate if you're in a hot climate or pregnant/breastfeeding.
- The calculator shows your recommended daily water intake in litres and glasses.
Understanding the inputs & results
Daily water intake
The recommended total fluid intake per day from all sources (water, food, beverages).
Activity adjustment
Sweat loss during exercise increases fluid needs — typically 500 ml extra per 30 minutes of exercise.
Climate adjustment
Hot or humid conditions increase sweat loss and daily fluid requirements.
The formula
Basic water intake formula
Base intake (litres) = Weight (kg) × 0.033 | Adjusted for activity and climate
A widely cited rule is 33 ml per kg of body weight as the daily base. Add 500 ml per 30 min of moderate exercise. Add 500 ml in hot weather.
Worked example
70 kg person, moderately active, temperate climate.
- Base = 70 × 0.033 = 2.31 litres.
- Activity adjustment (+45 min moderate exercise) = +750 ml.
- Total ≈ 3.06 litres (≈ 12 glasses of 250 ml).
✓ Recommended intake ≈ 3 litres/day.
Frequently asked questions
Water intake needs vary by individual health status, medications, and conditions. Consult your doctor if you have kidney disease, heart failure, or other conditions affecting fluid balance.