Water calculator
A daily target scaled to your body rather than to the number eight — and an honest note on how much of it comes from food anyway.
How this is calculated
total_ml = 30 × weight(kg) × activity_factor
rounded to the nearest 100 ml Thirty millilitres per kilogram is the clinical rule of thumb for healthy adults, and it is what the app uses as your default goal. The activity factor adds 15 % for a training day and 30 % for heat or hard physical work — round numbers, because individual sweat rates differ by more than any formula can predict.
What the number is not
It is not eight glasses, which has no clinical origin worth citing. It is not a score, and beating it is not an achievement — past thirst, extra water is just extra trips. And roughly a fifth of it arrives in food, so the amount you actually need to drink is smaller than the total above.
These are the same numbers and the same guards the Talk2Fit app applies when it builds your plan — the calculator is the app's own arithmetic, not a separate approximation.
Questions
Where does 30 ml per kilogram come from?
It is the rule of thumb clinical nutrition uses for healthy adults — roughly 30–35 ml per kg per day of total water. It is a starting estimate, not a prescription, and it is the same figure the Talk2Fit app defaults to.
Does coffee count?
Yes. The diuretic effect of ordinary coffee and tea is far smaller than the water they contain, so the net contribution is positive. Alcohol is the exception worth knowing about.
What about food?
Food supplies roughly 20 % of total water intake — more if you eat a lot of fruit, vegetables and soup. That is why this number is the total to aim at, and why hitting it purely by drinking is stricter than necessary.
Is more always better?
No. Drinking far beyond thirst dilutes sodium, and in rare cases dangerously. Use the number as a floor to notice you are under, not as a score to beat.