Water Intake Calculator

Calculate your daily water intake needs based on weight and activity level.

Water intake recommendations are estimates. Individual needs vary. Consult a healthcare professional if you have kidney disease, heart conditions, or other conditions affecting fluid balance.

Body Weight (kg)

Activity Level

Climate

Daily Water Intake

In Cups (250 ml)

In Glasses (8oz)

How It Works

Enter your body weight, activity level, and climate. The calculator recommends your daily water intake in litres and cups, adjusted for exercise and hot weather.

**Water Intake Calculator — Stay Optimally Hydrated**

Water is the most essential nutrient for human life. Every system in your body depends on it — from regulating temperature to flushing out toxins to delivering nutrients to cells. Yet most people don't drink enough. Our Water Intake Calculator gives you a personalised daily hydration target.

**How Much Water Do You Need?**

The baseline formula used by most nutritionists:
**Daily Water Need = Body Weight (kg) × 35 ml**

So a 70 kg person needs approximately 70 × 35 = 2,450 ml (about 2.5 litres) per day.

Adjustments:
- **Exercise:** Add 350–700 ml per hour of moderate exercise
- **Hot climate:** Add 500–1,000 ml per day
- **Pregnancy:** Add 300 ml/day
- **Breastfeeding:** Add 700 ml/day

**The 8×8 Rule: Myth or Reality?**

You've probably heard "drink 8 glasses of 8 ounces (about 2 litres) per day." This is a useful starting point but lacks scientific precision — it doesn't account for body size, activity, or climate. Our calculator gives you a more personalised estimate.

**Signs of Dehydration**

- Thirst (you're already mildly dehydrated when you feel thirsty)
- Dark yellow urine (pale yellow = well hydrated)
- Fatigue and difficulty concentrating
- Headache
- Dry mouth and lips
- Dizziness

**Water-Rich Foods Count Too**

About 20% of daily water intake comes from food. Fruits and vegetables with high water content include cucumber (96%), lettuce (96%), celery (95%), watermelon (92%), tomatoes (94%), and strawberries (91%).

**When to Drink More**

- Before, during, and after exercise
- In hot and humid weather
- When ill with fever, vomiting, or diarrhoea
- At high altitude
- When consuming caffeine or alcohol (both diuretics)

**Can You Drink Too Much Water?**

Yes, though it's rare. Hyponatraemia (water intoxication) occurs when sodium levels are diluted by excessive water intake, usually only during extreme endurance events. For most people, drinking to thirst is sufficient.

Frequently Asked Questions

A baseline of 35 ml per kg of body weight is commonly recommended. A 70 kg person needs ~2.5 litres/day, plus extra for exercise and hot weather.

Moderate coffee consumption (up to 400mg caffeine/day) contributes to hydration despite its mild diuretic effect. However, alcohol is a stronger diuretic and doesn't count toward hydration goals.

Excessive water intake can cause hyponatraemia (low blood sodium), but this is very rare in everyday life. For most people, following thirst is a reliable hydration guide.

Check your urine colour. Pale yellow indicates good hydration. Dark yellow or amber means you need more water. Clear urine may mean overhydration.

Yes. Add approximately 350–700 ml per hour of moderate-intensity exercise. High-intensity exercise in heat may require more. Drink before, during, and after workouts.