Water Intake Calculator
Calculate a general recommended daily water intake based on your body weight and activity level.
About this water intake calculator
"Drink more water" advice is more useful with an actual number attached. This calculator gives a commonly used starting estimate based on body weight, adjusted upward for activity level.
How water intake calculator works
The base formula used is approximately 33 ml of water per kilogram of body weight per day, then multiplied by an activity factor (1.0 for sedentary up to 1.6 for intense daily exercise).
Common uses
- Getting a starting daily water goal based on body weight
- Adjusting water intake targets for an active lifestyle or workout days
- Checking hydration needs for hot climates or increased activity
How to use this tool
- Enter your weight.
- Select your activity level.
- See your recommended daily water intake instantly.
What to know before using it
Individual fluid needs vary with climate, health conditions, and diet (including water from food), this is a general starting estimate, not medical guidance, especially for anyone with a kidney, heart, or other condition affecting fluid intake.
Privacy and browser-first processing
This tool runs entirely in your browser using JavaScript. Nothing you enter is uploaded or stored.
Frequently asked questions
Is "8 glasses a day" accurate for everyone?
That is a rough, one-size-fits-all rule of thumb, actual needs vary by body weight, climate, and activity level, which is why this calculator personalizes the estimate instead.
Does this count water from food and other drinks?
No, this estimates total water intake, roughly 20% of daily water needs often comes from food in a typical diet, so this figure is a reasonable target inclusive of all fluid sources, not just plain water.