Water Intake Calculator
Estimate your daily water needs from your body weight and how much you exercise.
How to use the water intake calculator
- Enter your body weight.
- Optionally add your daily exercise minutes.
- Click Calculate to see your daily target in litres and cups.
Hydration and performance
Even mild dehydration impairs strength and endurance. Drinking to thirst plus replacing measured sweat losses (see the sweat-rate calculator) keeps you covered.
How much water you really need
Needs vary with body size, activity, climate, and diet. A common baseline is around 30-35 ml per kilogram of body weight per day, rising with exercise and heat. Much of your intake also comes from food and other drinks, not just plain water.
Signs you are well hydrated
Pale-yellow urine and rarely feeling thirsty are good everyday signs of adequate hydration. During exercise, weighing before and after shows how much fluid you lost as sweat. Drinking to thirst works for most people most of the time; structured plans matter most for long or hot training.
Frequently asked questions
How much water should I drink a day?
A common guide is about 35 ml per kg of body weight, plus extra for exercise and heat. For a 75 kg person that's roughly 2.6 litres before training is added.
Does coffee count toward hydration?
Yes. The mild diuretic effect of normal coffee or tea intake is outweighed by their water content, so they contribute to your daily total.
Is the 8 glasses a day rule accurate?
It is a rough guideline, not a rule. Actual needs depend on your size, activity, and climate, and include fluid from food and other drinks.
Can I drink too much water?
Rarely, but excessive intake in a short time can dilute blood sodium dangerously, mainly a risk for endurance athletes overdrinking. Matching intake to losses avoids it.
Do coffee and tea count toward hydration?
Yes. The mild diuretic effect of normal caffeine intake does not offset the fluid they provide, so they contribute to your daily total.
Related tools
Sweat Rate Calculator
Work out how much you sweat per hour so you can plan hydration for training and racing.
TDEE Calculator
Calculate the calories you burn per day (your TDEE) to set targets for cutting, maintaining, or bulking.
Calories Burned Running
Estimate how many calories you burn on a run based on your weight, pace, and duration.