Free Water Intake Calculator - Daily Hydration Needs

Calculate your recommended daily water intake based on weight, activity level and climate. Track your hydration progress.

What Is Water Intake Calculator?

A water intake calculator estimates how much water you should drink daily based on your weight, activity level and climate. The common "8 glasses a day" advice is a rough guideline that does not account for individual differences — a 90kg athlete training in hot weather needs significantly more water than a 50kg office worker in a temperate climate.

General recommendations suggest about 30–35ml per kilogram of body weight as a baseline, with additional water for exercise (roughly 350–500ml per hour of activity) and hot weather. This calculator provides a personalised target and helps you track your intake throughout the day.

How to Use This Tool

  1. Enter your weight in kilograms or pounds.
  2. Select your activity level, from sedentary up to very active (athlete).
  3. Select your climate: temperate, hot/humid or cold.
  4. Click "Calculate" to see your recommended daily intake in litres, glasses and fluid oz.
  5. Premium: log each glass as you drink it to track today's progress and build a hydration streak.

Tips & Best Practices

  • You do not have to drink only plain water — tea, coffee and water-rich foods (cucumber, watermelon, soup) count toward intake.
  • Thirst is a reliable indicator for most people — if you are thirsty, drink water.
  • Urine colour is a simple hydration check: pale yellow is well-hydrated, dark yellow means drink more.
  • Caffeine has a mild diuretic effect but still contributes net positive hydration.

Common Use Cases

  • Calculating personalised daily water intake targets.
  • Adjusting hydration for exercise and hot weather.
  • Tracking daily water consumption for health goals.
  • Understanding how body weight and activity affect hydration needs.

Frequently Asked Questions

How is daily water intake calculated?

Your body weight is multiplied by 0.033 litres per kg, then adjusted for activity level and climate to give a personalised recommendation.

Can I track my water intake?

Premium users can log glasses throughout the day and see a progress bar tracking toward their daily goal.