Water Intake Calculator
A useful daily target is roughly 33 ml per kilogram of body weight, plus extra for sweat and heat. Get your number — then let thirst and urine colour fine-tune it.
How to use this calculator
- Enter your body weight.
- Add the minutes you typically train or sweat per day.
- Pick your climate — heat and humidity raise needs noticeably.
How the target is built
target = 33 ml × kg + 400 ml per 30 min of exercise ± climate adjustmentFor context, EFSA reference values suggest about 2.0 L/day (women) and 2.5 L/day (men) of total water — including the 20–30% that arrives inside food. Our weight-based baseline scales with body size, which the flat guidelines ignore.
What counts as water?
Plain water, sparkling water, tea and coffee all count toward the target — the mild diuretic effect of caffeine does not cancel the fluid. Food contributes another fifth to a third of total intake in a typical diet.
Frequently asked questions
Does coffee or tea dehydrate me?
No — regular caffeine drinkers build tolerance to its diuretic effect, and the fluid in the cup far outweighs any extra loss. Coffee and tea count toward your target.
Is it possible to drink too much water?
Rarely, but yes: drinking litres in a short window can dilute blood sodium (hyponatraemia), seen occasionally in endurance events. Sip through the day rather than chugging.
Do I really need 8 glasses a day?
The 8×8 rule is folklore with no scientific origin. Needs scale with body size, activity and climate — which is exactly what this calculator adjusts for.
Should I drink during workouts?
For sessions under an hour, water to thirst is enough. Long, sweaty sessions benefit from 400–800 ml per hour, ideally with electrolytes.