Water Intake Calculator
Find your personalised daily hydration target based on your weight and activity level.
How this water intake calculator works
The baseline is 35ml per kilogram of body weight — a widely used general hydration guideline. An activity bonus is then added: 0ml for sedentary lifestyles, 350ml for moderate activity, and 700ml for active individuals who train daily or work physically demanding jobs.
Practical tips
Spread your intake throughout the day rather than drinking large amounts at once. Start each morning with a glass of water. Use a marked water bottle to track progress. Adjust upward in hot weather or for high-sweat activities.
Frequently Asked Questions
- How much water should I drink per day?
- A common recommendation is 35ml per kg of body weight as a baseline, plus extra for exercise. A 75 kg moderately active person needs roughly 2.9–3.1 litres per day.
- Does coffee count towards my water intake?
- Yes, caffeinated drinks contribute to hydration despite mild diuretic effects. However, plain water is the most efficient source of hydration.
- How do I know if I am drinking enough water?
- The simplest indicator is urine colour. Pale straw yellow (not colourless) means you are well hydrated. Dark yellow suggests you should drink more.
- Does water intake affect exercise performance?
- Yes. Even 2% dehydration can impair aerobic performance. For sessions over 60 minutes, aim to drink 400–800ml per hour depending on sweat rate and temperature.