Water Intake Calculator
Fluid needs scale with body size and with how much you lose through sweat, which makes body weight plus activity a reasonable basis for a target. This calculator returns the figure in litres, fluid ounces and bottles, and separates out how much needs to come from drinks rather than food.
Your result
Fill in the fields on the left and your result appears here.
How the target is derived
The baseline uses roughly 33 millilitres of fluid per kilogram of body weight, a common working figure for healthy adults. Activity adds to it, because sweat losses are the largest variable component and scale with duration and conditions rather than with body size.
The distinction between total fluid and fluid from drinks matters more than people expect. A meaningful share of daily intake normally arrives via food — fruit, vegetables, soups, yoghurt and most cooked dishes all carry significant water — so a total-fluid target is not a drinking target.
- Around a fifth of typical daily fluid comes from food, which is why the calculator separates the two.
- Hot or humid conditions, altitude, illness with fever, and alcohol all increase requirements beyond the activity adjustment here.
- Urine colour is a more honest day-to-day indicator than thirst, which is an unreliable signal even normally.
- Anyone eating markedly less than usual is losing the food-derived share too — a reason fluid intake quietly falls during weight loss.
Track it, don't recalculate it.
Pep AI logs your weight, meals and protein alongside your schedule, so the numbers on this page turn into a trend instead of a one-off. Free on iOS and Android.
Where a general target stops applying
This is guidance for healthy adults with normal fluid handling. Several conditions change it entirely: kidney disease and heart failure often come with a clinically restricted intake, and in those cases the restriction is the target, not this number.
There is also an upper end. Consuming very large volumes of plain water in a short period can dilute blood sodium, which in extreme cases is dangerous. It is rare and generally requires drinking far beyond any sensible target, but it is worth knowing that more is not indefinitely better — steady intake across the day is the sensible pattern.
Frequently asked questions
This calculator is general information for healthy adults, not medical or dietary advice. It applies published population formulas and cannot account for your clinical situation. Where a clinician has set you a target, that target replaces this one.
Built by the Pep AI team.