FREE TOOLS
How much water you actually need
An adequate-intake estimate from body weight, exercise and climate — and a straight answer about how little the science settles.
Be careful with any number here, including this one
There is no single accepted formula for how much water a person needs. What exists are adequate-intake figures: the European Food Safety Authority and the US Institute of Medicine put total water at roughly 2.5 litres a day for men and 2.0 for women, and total means everything — drinks, and the water in food, which is about a fifth of the total. This tool takes the larger of that figure and 33 ml per kilogram, then adds for exercise and heat.
Thirst is a better guide than arithmetic for most healthy people. Pale straw-coloured urine is the simplest check there is. If you have heart or kidney disease, or you are on diuretics, your fluid target is a clinical decision and not one a web page should make.
This tool gives an estimate for general information. It is not a diagnosis and it does not replace advice from a doctor or a dietitian — particularly if you are pregnant, under 18, an athlete, or managing a health condition.
